The wait depends on the amount used plus the half life. It only takes 3 weeks for a 500 mg/wk cycle to get down to 62.5 mg but it takes 5 weeks for a 2000 mg/wk cycle to reach the same level.
2000 mg Test E/wk vs 500 mg/wk (half life 7 days for sake of argument)
2000 mg/wk cycle:
Week 1, 2000 mg/7 days = 1000 remaining
Week 2, 1000 mg/7 days = 500 remaining
Week 3, 500 mg/7 days = 250 remaining
Week 4, 250 mg/7 days = 125 remaining
Week 5, 125 mg/7 days = 62.5 remaining
500mg/wk:
Week 1, 500 mg/7 days = 250 remaining
Week 2, 250 mg/7 days = 125 remaining
Week 3, 125 mg/7 days = 62.5 remaining