Yes.
I look at a provider's schedule to see if they're working a reasonable number of days a week, and a reasonable number of hours a day. If a provider is doing a long shift I usually aim for the first part of it. That way they're more rested, and with less of a chance of having seen a bad client before me.
IMO, sex work isn't really the kind of work where doing the typical 5 8-hour shifts a week is sustainable over the medium to long term. It's a job that is mentally and physically taxing, at a minimum. I like engaged sessions, with a provider that still has some mental and physical gas in the tank. If you want to improve your odds of that then factoring in how much a provider is working (and where you land on a shift) is a good idea.
Edit: I don't really have a hard and fast rule on 'too many hours'. If things start getting toward a 40 hour week, or more, then it becomes an increasingly big factor when it comes to booking.