I think most people can do well on 500mcg to 1 mg. 3 mg is pretty high and likely represents a level above and beyond endogenous production...but that's just my speculation.
Used the night of workout days, it really helps with recovery. The estrogen thing is a big bonus IMO. There's probably a relationship between lowering melatonin levels as we age and rising estrogen levels...at least it's part of the bigger picture.