I've ever been to any PV provider. Is it best to book the full hour or is 30 minutes sufficient? I feel like I read here, or on another board, that 30 minutes was all it was worth. Is it all down to personal preference? Sorry if this is a dumb question.

There are no stupid questions only stupid answers. Here's one. I don't know about now. The last I saw one was 2000. Late 90's there were 3 extremely hot PV providers in the area. I saw them and 2 of them I saw many times and never for 30 minutes even on the first visit. Why? Because if you hit it off with them there was so much more available, but I never recommend them for anything other than PV, so somethings are in all reviews. Today, I don't see anything to compare, a few agencies. Depends on the ladies, money you want to spend and what they are willing to do. From what I've seen in reviews, 30 minutes would be a good start and be ready for some up selling.

There are inappropriate questions, though.

First, the 60-minute rate is less than double the 30-minute rate.  Depending on the agency it's $200 v. $120 or $220 v. $140.

Second, the PV places really are limited by room availability.  In a sense, you are paying to rent the room for your allotted time.  Thus, time limits are rigidly enforced.  The time from when you get the ok to when you knock on the door is 2-3 minutes.  It takes another 2-3 minutes for the girl to check the money and come back.  It typically takes 2-3 minutes or more to get cleaned up and dressed.  That turns the 30-minute session into 20-22 minutes and the 60-minute session into 50-52 minutes.  If you are the kind of guy who is raring to go and happy with 15 minutes, then save some money and do the shorter session.  For me, though, it feels far too rushed.

Third, I think the menu is a function of the length of time booked, both because of the length of time together and the amount you pay.  A PV girl is more likely to give you extras if you pay the hour rate and if there is enough time for extras.  In a 20-minute session, it's highly unlikely to get DATY and almost impossible to get BJ.  

Fourth, the 60-minute date allows the opportunity for 2 cups, which I've taken advantage of some times.

I'd recommend the shorter session only under the following conditions:  Money is really tight and $120/$140 is all you can manage.  You are satisfied with 20 minutes of play and can finish within that time.  You just want to see what the girl looks like in person.  Otherwise, I'd strongly recommend the full hour.

I always book 30min initially as I figure low initial investment to get a sense of if pics are accurate and chemistry.  Extras definitely can be offered despite the short time but it really is a 22min appointment by the time she walks back.
I've never tried to extend during but I'm sure they won't be opposed if there's no appointment immediately to follow. More often than not, I book a hour on future visits after sampling the wares

Seeing the woman in person gets you valuable info.  The shorter initial appointment makes sense.

For the agency that shows the faces of the girls, I think seeing them in person is less critical.  For other agencies, it can be important.

 
5 mins early is on time so you can walk to location & she has time to count the money. Unless it was busy & girl didn't have sufficient break to get ready I normally get full time as scheduled unless she counts the time when I entered instead of the official time....which rarely happens.

Since we talking PV here interesting girls to see out there?

I have no new intel.  Sorry.