I have done this for extended periods. I have ED issues at times, even on TRT, which I've been on for about 7 years. Masteron has helped me with that tremendously. But I had to use pretty high doses for it to be effective. That said, I've read that for Mast to be effective, high doses are required. My experience tells me that's true.
This was my protocol when doing this:
Mon and Fri: 100mg test cyp; 30mg test prop; 50mg Mast prop; 300mg Mast enanthate.
So, total of 230mg test and 700mg mast per week.
I did other variations on the above theme, but to keep it simple, that's what I was doing. I did that for 2 years straight. I am 49. My hair did not fall out. It did not get any thinner on top than it was 2 years ago. No negative effects on my prostate according to the PSA number as well as the annual ultrasonic inspection my urologist does. However, I did grow a lot mpre body hair, especially on my shoulders and back. That was -is - the only negaitve side.
It also had the effect I was looking for: it helped the Dangling Disappointment show up for work when it was time. Overall, it was a very good experience and I wouldn't hesitate to do it again if I feel like I need to.