I usually book 30 mins for a first visit just incase its not to my liking, so I always go in with the idea of checking out as much as I can in the half hour and if I like I will book an hour another time. On the occasions I have gone back a second time for a half hour I find myself rushing things or, more preferable, limit the services I partake of and cum bang on 30 mins.
I think an hour is perfect as it lets me sample a variety of services, try the ones I didn't have time for before and plan when and how I want to cum. If that means cumming early and enjoying a nice chat, clean up or FK and a cuddle afterwards, all the better. Pricing is also better value as a rule for a longer booking. For me 45 mins is neither one nor the other, but I might be tempted if the price was right