Its such a good thing that this is an experiment. It is your body and you are already identifying how it responds to compounds and in what timeframe. If I were you, I would either switch to sustanon altoghether, or do the test-e until the gains start to peter off, and then switch to sustanon for several more weeks.
I would plan on a good long next cycle if I were you, like maybe 20 weeks. Throw in a good 400mg of Deca each weeks, and up the test to 750mg..... add in some d-bol in the front and eat some winny in the back...
Dude, I cant see how you could stop gaining on one like this......... by the way, my gains petered out on test-e after about 7 1/2 weeks,...... I started taking sustanon and I started gaining again and quick too.... hell, Im having trouble knowing I have to come off when I finish up this sustanon...... but my next cycle will be a monster......