I think it also depends on your general physical condition and current level of expertise. I have shot a couple of "mega-sessions" mostly to test pistol or magazine function in a new or newly repaired pistol. But I find it very tiring. My routine now is to try to shoot under 200 rounds per session, load my magazines 5 rounds each and 10 rounds per target (two mags). Were I to acquire a new pistol from my wish list I would back off on the "new kid" but fill my range time with my Ruger or GSG .22.
I try to get to the range an average of three times per week but am averaging closer to twice per week since I started keeping track of things.