There is a thread that tells you how to calculate a pitchers "real life" pitches/ season and pitches/ game. However, I usualy look at the pitchers IP/G and multiply by 15 or 16. That is the max pitch count I'll alllow on any given pitcher.
I then work down from these maximums to get ~7 ip/ game from my starters and split my innings between the starters are the bull pen such that 75% of my ip is in the rotation.
For starters, I set the typical pitch count 10 less than the max setting and for relievers I set typical pitch counts 5 less than the max setting.