There have been many times that I've seen a provider a day after and a few times, three days in a row. The number of rounds usually is limited to one per hour but on occasion, multiple rounds can be done in 2. It's just a matter of hydrating and keeping up on the vitamins.
I would like to mention that there have been a few times that I've left a provider after one round and got so aroused as time ran out, that I went right to the next one to satisfy the craving. The option to extend is there if no one else is booked which I've done as well. Again, it's all about energy level and how well the provider can get you motivated. Suffice it to say, with a bad provider (not a rip-off), I've left totally frustrated and unable to hook up for a day or two. As long as i can do it, I will - why put off thinking about it - just do it and see how it goes.