Dry times depend on equipment and how many dry passes as well as time of the year.
Here in WA in the summer when it gets hot with a portable and a 360i I can get 6 hr or less dry times. When it is nasty weather it can go as much as a day.
I hook directly to the customers sink so maybe 35psi. With the rotovac you do not need heat because you have agitation. If you connect to heat you may have quicker cleaning though. Rotovac 360 has 3 spray jets so be careful with psi.
I have 2 360is and I broke the frame on both of them at the welds and had to have it rewelded but other than that all you have to do is replace your felt seal. Every now and then I will open the head and make sure nothing is gummed up in there. I have had the seal in one of the heads replaced and the other is due the suction tends to pull in the sides by the vac ports over time.