the amount, a person drops from good people, is irrelevant due to our bodies half life system. Here is a great explanation of how this works. Not being a dick so give me a pass as i'm in the know here. so here is how half life and substance elimination works... but you have to take into play the weird nature of methadone.
but methadone has a really subjective half life.. in other words its quite varied with an individuals physiology. A good average is two weeks.. but the longest seen is 120 days.. so thats a half life of 120 days.. x five is the elimination.. thats huge as far as any drug. I think it has to due with a subects specific genetic enzimes.