If it's a girl I've seen before and like, I usually book 90 min to two hours.  But two hours can feel like an eternity with a girl you don't click with in person.  So I've found 60-90 min is good for a first time session.  Although I have been known to book a 90-minute starter session and extend it to two hours if it goes well.  If you do that, you have to remember to have enough extra cash on hand and you also have to accept the risk that she might not be able to extend due to other commitments.  Good luck!!

s others have alluded, there is nothing worse than paying for multiple hours with someone whom after five minutes you have no interest in being with. For new hobbyists, I would recommend an hour for a first time visit. This should be enough time to gage whether there is chemistry between you two and whether she is someone you'd like to see again. Yes,  I have done several first time dinner dates (4 plus hour appointments), but I was fairly confident based on the ladies review history and my own instincts that we would be compatible. I have been fortunate to date to have had really good experiences.  But most of my first time appointments are an hour.  

Unless you are someone who has trouble relaxing and your nervousness will prevent you from "rising to the occasion" within the hour, I think 60 minutes is a perfect amount of time for an initial visit.

8 to 9 inches, on a good day

then a gal told me that an hour was fine & we'd finish what we started...  been 60 since then.