Biological facts:

1. Muscle tissue will atrophy without use and exercise.

2. The prostate, while specialized is muscle tissue.

3. The vast majority of the medical community agrees that a reasonable amount of sex (3 to 5 times a week) keeps the prostate healthy and prevents prostate cancer in older men.

Web MD article
[link to www.webmd.com]

Harvard Medical article
[link to www.harvardprostateknowledge.org]

If you want to believe in superstitions go ahead, but I'm sticking with facts and evidence.