It isnt about how long you lift. Anything over an hour for most people is overkill. Cortisol, the muscle wasting horomone usually begins to rise around the one hour mark. My workouts only last half hour, and sometimes even less. IMO, Intensity is the key to strength and hypertrophy. While you will get differing opinions on growth, most will agree that the quicker you get in and out of the gym, the better.