This is unacceptable, to limit your sessions to 15! One definitely needs more than that to clear, although if you do bj's formula at the same time you can cut down on total sessions needed.
Ideally, maintenance treatment of one session a week is good to maintain the clearance, because if you stop the P will come back quite quickly for some people (like me!)
I also stay away from Dovobet, but i use Dovonex.