Phera-Max has received terrible reviews from users. The consensus seems to be that it is underdosed or inert.
With that said, assuming it worked for you 3 or 4 weeks is the standard cycle length for pheraplex compounds.
A SERM is always recommended. You don't just take the SERM for gyno, you take it to restart your natural testosterone production which slows-down or stops when you introduce exogenous hormones into your body.