I am in favor of clearing the tubes on a steady basis. Several times a week from my point of view is fine.
Climaxing with a partner would be optimal but I really think keeping those pipes clear helps, solo or with a partner.
I was personally more once a day but it has tapered off due to some changes. Nothing "dramatic", just that my schedule seems to be quite wacky. LOL
Enough masturbation / moderate amount doesn't cause ill effects. I really feel once a day can be pretty safe for most men. Some get blue balls if they don't release on often enough, there can be slight hormonal changes as well. "As always" there is a golden middle ground, moderation.
When to stop? When it hurts, takes too much of your time and is more of an addiction than a fun blast here and there.
The gains question is probably the most popular one. One can target length after ejaculation (orgasm and ejaculation are two different things by the way ...) so that's one thing to remember.
Then again for girth gaining a strong Erection Quality is important so it could be wise to space out girth and length routines if possible.
Of course a possibility is to do a strong girth routine, blast off and do some length exercises, although it might be more difficult if there's a lot of temporary gains from the girth workout.
There are many ways.
If you're not masturbating in excessive amount
(what people see as excessive is different of course, I'd say 1-3 times a day could be normal for a young guy, once a day is) then I wouldn't see a problem.
Thanks for making the thread, it's an interesting subject!