hmm, I am over 40, my natural test is probably low average to low.
My results from a test only cycle have been extremely good although I seem to have peaked in weight gain around 9 weeks @ 600 mg / day.
I'm going to do a full pct and see if I can hold most of the muscle and then concentrate on getting my bodyfat down around 10% before I take another serious run a gaining size.
I don't think I've exceeded my "natural limit" but I am currently at the highest bodyweight/strength (outside of my damn shoulders).
I am very much considering a 200mg/week bridge but won't decide till after I see how/whether I am successful with my PCT this time.