It depends on what you're practicing with. Lobbing more rounds down range isn't always better, because there's a point where fatigue will set in and technique will suffer. In general, the more energetic the felt recoil of the gun, the quicker you'll reach that point.
For me, I like to shoot 50-100 rounds per session from a gun I find comfortable to shoot, or 20-30 rounds per session from a gun I find unpleasent to shoot. I also like to keep the total count for a session (if I'm shooting multiple guns) to no more than 100 rounds of centerfire handgun ammunition.