I'm not sure I understand the question, but I'm guessing that what's really meant is: How many times a week do you masturbate in such a way as to have a prostate orgasm. I mean: When I do that, I usually have ten to twenty, somewhere in there, but it's all in one session. I think that's pretty common. Once you have one, you can keep going.
So the way the question's asked it's got to be: How many sessions per week?