Ok, I like 90 minutes, an hour is too short, I always feel rushed. Two hours is too long, I'm always left with time on the clock. And sometimes I get three hours and go dancing.
I'm also budget minded, therefore I always try to chose a girl that offers a multi hour discount. That is when you purchase more than one hour and the total is less than if you had paid the hourly rate times the number of hours purchased. For example:
If 1 hour is $300, then $550 for two hours would be a $50 discount. (300 x 2 = 600 - 550 = $50 discount.
But some times I will see a premium for multi hours. For example:
If 1 hour is $300 then 90 minutes should be $450 ( 60 x 1.5 = 90; $300 x 1.5 = $450 ). If your rate is $300 for an hour and your 90 minute rate is $500; you are charging a $50 premium. If you wanted to offer a multi hour discount it should be less than $450.
The same goes with three hours. If your rate is $300 per hour then 3 hours should be $900. ($300 x 3 = $900). If your three hour rate is $1,000 then you are charging a $100 premium.
Now of course if you do not like multi hour sessions, or dinner or dancing dates, then charging a multi hour premium makes sense, but most of the sites I read say girls like longer dates. Personally for me, I would never book a girl with multi hour premium; and while I have considered it for some girls, I have yet to book a girl without some form of multi hour discount.
I hope this information is helpful.