Normal time is 30-90 seconds. The heavier weight wise you go generally the longer that time goes
-------------- As a quarter squatter was dominating the rack, I heard a conversation between an old powerlifter (easily in his 60\\'s) and what I would guess was his grandson (15-yrs old):
Kid: \\"So, why does he stop so short on his squats? That looks weird to me.\\"
Old PL\\'er: \\"He\\'s afraid if he squats deep, his vagina might touch the ground.\\"
Depends on your goals. Use your 'recovery' time as a guage. Not more than 3 minutes though, as research shows that longer does not really provide any significant advantages. Heavy weight, as Mutt mentioned, rest longer periods to recruit as many muscle fibers as possible for the next heavy lift. Shorter for weight loss/cardio rivaling workouts. More muscle endurance.
-------------- Baseball is the only field of endeavor where a man can succeed three times out of ten and be considered a good performer