I go from 1-1.5 hrs. Depends on how my body feels. Just listen to your body, it knows when you need to stop. However, if your all jacked up on speed I guess that could be a problem, LOL! I wouldnt go no longer than 1.5hrs maximum.
__________________ Goal= 220 lbs. by Aug-08
Current= 204 lbs. as of 4-08-08
Bench: 255lb. x 2
Dead: 310lb. x 1
Squat: 350lb. x1
Hitting the road hard and Im not F'n looking back till I hit 220!
Yes, 30-45 min is ideal according to a test done that showed in an average male test and GH levels peak at about 45min of activity and then slowly start to decline after that.