Well for me, with zerg, it totally depends on the game... The big difference is that I don't really think in terms of drones, but in terms of larvae. The more drones the merrier (and zerg rarely saturate since they tend to me expansive anyways) but you constantly have to balance your drone production with your army production. Once the early game is over though, I tend to make drones in large batches (like after a big battle where armies were traded, always make drones).
... Or at least this is what I try to do^^. I'm a pretty bad player but I just watch lots of games and try to apply whatever I know as well as I can
