8 - 12 weeks.
The routine goes as follows:
Day 1
Squats - 3 x 4, 6, 10
Deadlifts - 3 x 4, 6, 10
Overhead Presses - 3 x 4, 6, 10
Weighted Dips - 3 x 4, 6, 10
Day 2
Rest
Day 3
Dumbbell Rows - 3 x 4, 6, 10
Decline Bench Press - 3 x 4, 6, 10
Weighted Chinups - 3 x 4, 6, 10
Leg Curls - 3 x 4, 6, 10
Day 4
Rest
Day 5
Rest
Day 6
Repeat Day 1
You may want to take two day's of rest after each workout or even just make the routine a two day a week program (for example, Monday and Thursday), as it can quickly drain you of your recovery ability and energy if you are working the program as hard as you should. And if you are interested in building muscle mass, you need to work the program hard.