Before this goes apeshit with responses of "me too. I got extra time. I'm SO special" let's break it down to your actual question.

"How should a repeat be handled?"
Simple. You handle every future appointment for exactly what you asked and paid for. Done.
If you get more, great. If you don't so what.
Ultimately it's her choice what to do with her time. The second you go in expecting something more than the black and white arrangement, you become a douche.

It would be nice to leave a tip if you can afford it. Frankly if you can't even afford a tip you really shouldn't be doing this, but that's another story. Again, don't over-complicate. Don't be like these ass-jacks who get into issues with offering, how to bring it up, what do I do? It's sickeningly stupid.
Just excuse yourself to the bathroom right before you leave and set it on the counter. It will most likely never be spoken of but definitely appreciated.

None of this stuff is hard, people just try to make it so.

Personally, if I am comfortable with a guest, enjoying myself and don't have other immediate obligations or a rest period scheduled I'm not especially concerned with watching an egg timer.

However, I am appreciative and impressed when the client is cognizant of the time and appears concerned about "overtime".
My rates and my scheduling are set by myself- I don't have an expectation of receiving paid acknowledgment/tips- if I allow a guest to stay longer than agreed upon it isn't a task and I am not hoping to be compensated for it...but then again I am the sort of provider who will expressly say when I expect an appointment to be formally extended.

I say just be nice, go with her flow, don't expect each appointment to be a 3 hours for 1 experience and ask her from time to time if you're overstaying your welcome.

Stop waiting around for her to forcefully shove you out the door. You know how long you booked her for. Its bad for business for us to fling your shoes at you and tell you get out, but that doesn't mean we aren't waiting patiently on you to start putting your clothes on and making a graceful exit.

This has happened to me with three different providers. I booked an hour (as I almost always do). Two went for 2 1/2 hours and the other one was close to two hours. There were never any hints that they wanted to wrap things up. In fact, I was asked if I wanted to go again in all instances. My question is: How should a repeat be handled? I'm not looking to take advantage of anyone, but if they are willing to give, I'm willing to receive. I book one hour appointments because that is usually what I'm comfortable with spending so the option of just paying for the extra time anyway isn't really an option for me.

All responses are welcome, but provider responses are VERY welcome.

If I brought extra cash, I would give a tip if the session extends a bit and we enjoyed each other.  If you don't carry extra cash, then give a great prompt review will also do. Anyway, a repeat visit is something I would do if this happens.  This happened to me too - a lady extended to 3 hours (she wanted to take her time with me) and I didn't have extra cash, I asked her if there was anything she wanted.  We drove to a store very near the hotel after the session, and she got a pack of cigarettes, a pastry, and a juice drink, so I put that on my credit card.  

It happens to me often. One girl doesn't let me leave until I've been there 5-6 hours , even though I only pay for one hour. I tried to tip another girl after we went over (she initiated a second round after the time was up), and it was awkward and I think she was offended. Just be happy they like you enough to keep you around is my advice.

I took her out to eat after we were done. That was my first time doing that, and it was fun. It let me see another side of her.

"if you can't afford a tip, don't do this"?  WTF?  and guess what?  I get extra time all the time!  sometimes they pay me, Graabir.  sorry everyone isn't as quick on the uptake as you, my little friend with the trust fund.

Fair comment.  It really is also the client's responsiblity to be aware of the time, too, and not put the burden completely on the provider.

"In fact, I was asked if I wanted to go again in all instances."

Personally, I leave when my time is up (and I usually HAVE to go)... if I was specifically asked, I would consider staying longer.

I would also give future business with nice tips as a way of showing my appreciation.

because that is some great karma you have going there.

or bring a nice gift. Why is it so hard?

...playtime, i always thank them by booking another session. I'll usually book the same (an hour) and pay the rate asked, but I also bring along something nice for them -- a few bottles of wine, maybe a bottle of their perfume I noticed while showering in the bathroom, etc.

While I don't expect "bonus time," I'm grateful when it does happen and am happy to return the favor(s). If it doesn't happen, then I've at least gotten what I paid for and I'm still grateful. Win-win scenario --

Agreed!!.....thank you for stating the obvious that's seems to over-looked and not considered!!

you must be doing something right because if these ladies are allowing you to stay longer they just like your company and are having fun. they would give a quick hint if you were staying too long, but i guess a nice gesture might be to bring a bottle of wine, or some flowers, just something to say i appreciate you appreciating me as wel...l if a lady likes you enough to have you stay longer. have fun