depends how hard you push...pick a cold tire starting point, say 32 psi, now ride until they are fully warm, which will increase the pressure. You only want them to increase about 2 psi between cold and hot...so, lower pressure will run hotter, pushing harder will run hotter, running hotter will increase pressure...
or, stock 550 pressure works fine for general riding and probably best durability. Some folks feel that is a pretty mushy feeling and you get a better feel around 32-37psi...this is where you stop using the tire as a crutch for poor suspension