Test,beyond the 1.5 gram/week mark,seems to give diminishing returns for most,unless you're a pro who has been using massive amounts for years on end.Deca,at beyond 600mgs/week seems to give more sides than it's worth.
You can get a pretty good idea where the point of diminishing returns are just from listening to the feedback on these boards.If you take in enough data from a large amount of differing users and weigh it,you will usually start to map out a pattern.