I can't really say which appointment length is my favorite. I get many more hour long bookings than anything else, but I offer everything from half hours to overnights. The hour long is a nice time to chat a bit, get physical, and then chat a bit more, but I really hate when I get the guys who want to fuck for an entire hour and that really drains me (and can be painful). The half hours are nice and quick and the guys come in and get to the chase, and I glance at the clock and time is up! That's awesome when I need a little break and I feel like I get a lot of money in comparison to the effort I have to put in. But then with a client I enjoy I really like the earning potential of a longer booking and being able to take one appointment for the day and be done. Again, with some clients who just wanted sex for 2-6 hours or were incredibly boring that would be torture, but I don't at all mind clients who want to talk about random stuff even if I'm not interested. Anytime I'm being paid ridiculous amounts of money to lie in a comfy bed and listen to someone talk I'm pretty happy. Even overnights can be nice with the right client, and you walk away drained but with enough to pay your rent and then go shopping!
I guess if I had to pick I'd stick with the hour long booking and my inner clock is trained to know exactly when an hour is up, but I enjoy having a mix so there's no monotony. Any length of time with a horrible client is too much, and with a wonderful client I could happily spend the whole weekend haha. If you really dislike anything except an hour long booking then definitely only take hour long bookings or decide how much you'd need to not dread another length and charge that rate for non-hour long appointments. If you're happy and enjoying the client that will show, and adversely, if you're counting down the seconds til you can bolt that will show, too. So do what makes you happy!