Part B. varies greatly. Prob some lump sum that allows  them to not work for awhile

No, really, there's no set way to figure it out.  It depends on whether she likes doing them and wants to encourage them by offering an attractive rate.
I've never done one and have no real desire to, because I fail to see the value in paying someone to sleep next to me.  I also have no desire for morning sex.
Last, it's a humanitarian gesture.  I won't inflict myself on her because in the morning I look like this

for  others  not so much. Everyone has their own style. Best thing to do, is try an overnite, preferably with someone you've spent time with before. If she doesn't have an overnight rate posted anywhere than ask.  Some will give you a screaming deal, because they may like your company, other's will charge an arm and a leg, because they don't like to do overnites.   There's a certain provider in the OC, if you do an hour outcall, there's a good chance if she's having a good time,  she'll spend the night, no charge. Just make sure to tip her well.  

I only do it out of

curiosity about getting the full girl.    whether it is worth it depends on how many hours she plans to sleep versus how many pops she plans on giving me multiplied by the ratio of her hotness weighted by her performance.  There's also the pillow talk and hangout time weighing in to the equation as well,  but you need to use binomial expansion and cut out the higher order terms that may not contribute all that much to your session with her.  Careful  not to get caught up in a Taylor series if she constantly yacks.  suggest she give you head in that case.  

I usually can't sleep all that well next to a pretty stranger even if I had seen her for a few sessions.  

If she is someone I'm very comfortable with then it's different,  but then if it's someone I'm comfortable with to that extent I usually won't be paying to sleep with her.

Fk no it ain't worth it!

You gotta learn how to game the system. Book her for a 2-3 hour session at night and have her come back in the morning for another 2 hour session or so.

You'll save TONS of cash, have a great night's sleep, get your much coveted morning sex and you won't have to watch her sleep and listen to her snore.

In this game, you can have your hooker and eat her too!

Comparing a 12-hour, and the nature of the experience to a one to three hour session doesn't work for me. If a three hour results in two long rounds and two pops, I don't therefore assume that in 12 I'll have 8. Instead, it amounts to a longer visit, more talk, drinking or whatever, and waking up to a beautiful woman. But it's such a different type of thing that I enjoy it as an experience. Apples/oranges.

And, the discount has to result in the price of two long sessions. That makes up for sleep time. So if three hours are 1k, twelve ought to be around 2k.

And ADJ is right. If the lady likes doing overnights, she'll set a decent rate.

Every overnight I've done has gone way over the clock. Going out for breakfast or just long talks while showering, getting dressed and sipping coffee (or tea, juice, whatever). OTC? Kind of, but not really. More like just hanging in a coffeehouse.

Considering the women you see, no, doing an overnight is a waste of time and money.

In my personal opinion.  Waste of money and the next day you think it was a utter waste of money.  Just my opinion though.

hours straight. i cant go longer than that . thats like my max.  
If i did an over night i only have several times with one regular on here. I charged i think once he gave me 1600 or 1400, But we only do about forty five min of actual sex.  
so. i know i know , its for our time.  
                 I have never had any takers on the five grand to have a sleep over and hang out with me thing. I guess i am not that cool!
 Not to say i havent made the attempts ran the eros vip ad got the good reviews. I definetly wouldnt lead them on though i d want to be straight about how much actual sex i d be doing thru out our sleep over.
 i know for me i do not wanna be woken up mid sleep to have sex. I d be ok with max 2 hours of sex. or if less sex like say an hour, then i d over compensate with say 2-3 hours of good deep massage and spa treatments.  
I always assume the girls getting tons and tons of money for over nights, are also staying available for sex antire time. i am not willing to be avl. for fucking at any time for a whole evening, so for me i think 1000 for a sleep over with a regular bne ok by me. or 1000 for off clock with regular ne cool with me, to me thats alot money for a day. for me also i only have a certain amount of stamina, i personally dont charge alot extra fro social times and dinners. i probly enjoy that as much as the clients. I d rather get to know a guy that just gave me a grand than waste my time with a civvie guy who treats me like crap. i d rather build closer bonds with clients. I have grown to really really enjoy a very smal small handful of my clients. i like kinda being coerced or bribed shall we say to act out wilder scenerios and acts i may not other wise do. i kinda like the whole set up, and find it more a turn on,  
 i would do a over night with a new clients for 2 grand, and any of my regulars 1000 for otc whole day or over night be more than enough and i d actually be pretty dam stoked, i had an otc last sat for 1000 . and we never do it for that much so i was pumped. i never ask him for that much but i made a mistake of abandoning my bills to "move to jersey" and when i came home , i realize all the bills are piled up and my rent. so i kinda hit up every one as of late a tad more,  
 i hope i dont get to used to it! hahah.
i am keeping the rates this way now any ways.  
'i compare my looks service over all experience, to this other lady, she is i feel alot prettier, and alot better performance scores so i imagine she is better in the sack than me, i seen she gets 1,400 for 2 hours, so i was thinkin, geesh, i suppose i wouldnt feel bad askin for 900 for 2 hours, if this chic gets 1,400 for 2 hours, i d say 500 less than her be about fair, i based my thinking on that, . i had some guys argue over my new rate and that was what i said i said i am not as successful good at this as her, granted but but i feel i deserve at least 500 less than her. and dont care if they dont like it, so far i had 2 takers, so, thats was enough to make me have it be kept the new menu rate.
 me personally I would have to straighten out how long are they looking to be bangin and attacking each other.... i d have to make sure they knew my limits , and granted i just dont like the whole idea of asking for a trcukload of cash to chat with some one who already just gave me a grand, if some one gave me a grand i am more than grateful and am more than happy to get to know them establish a repoire, in hope theyl come back and give me a grand a second time and a third time,
 now i  know one lady that get a grand an hour, one my regulars he comes with a grand every other month plus gifts , plus dinner, shopping sometimes too, and is so easy we only have sex for 45 min maybe? not much strenous . now he sees me every other month for about 2 years now.  
but her on other hand he seen her once. so you do the math, you can charge up the ass and guys may not come back, they may leave and feel like they just made abad choice and over spent. or you can be somewhat not so pricey and alot will say hey this is great deal, i had fun, i will go again to her next month and return maybe every month for years to come, in long run, having lower prices for me has pannned out quite well i have no complaints, .......................i have one regular for 7 years now who spends over grand every month like clock work, which is pretty much the entire rent out the way, or he spend 500 a week which is more than the rent, the rent is 1800. {bastards raised it this year , gotta love boston rent}
i d say its worth it if  you ll enjoy yourself and thwe person, have alot of fun, and as long as the lady is not out your price range, if you cant afford a professional model, or national top 100, like you may not wanna spend the mortgage and feel bad after, maybe a regular your close with will give you a special discount like i do with my reliable regulars i had for years now. . i would definetly do 1000 for over nights or otc, with regulars but thats as low as id go even for good regulars you gotta draw the line somewhere and have your rules. you also dont wanna be puttin yourself out, i know after an otc or over nigth i am mentally drained and have alot of cleaning to do. i like to sanitize bath tub with bleach ect ect before any new guy comes in, just like they would at a professional spa or massage parlour.

Lot of good comments here.  You have to decide what you are expecting in the overnighter.  She should be someone you've seen before.  As mentioned it wouldn't be 12 hrs of continuous sex.  So you should have some chemistry with her.  I've only done it a couple of time and have always had a great time.  As mentioned the rates should be adjusted so you're not paying to see her sleep

As long as you are compatible, go for it. Ask her what her rate would be for an overnight. It's usually discounted to some extent.