A couple of years, to be honest. I was in a celibate marriage, work-stressed, on libido-killing anti-depressants, and had absolutely nothing sexy in my life. I didn't even miss the desire to do it.

Hope to never do that again.

5 days maybe

Sometimes, for me, weeks go by without even thinking about it.
Generally though, it happens for me about once a week... Well, in the classic sense at least. I often enjoy a little anal play, but it's not usually paired with penile masturbation. That might seem odd, but I find the former more satisfying than the latter, and I don't require the typical climax (ejaculatory orgasm).

40 days. I tried it after watching that Josh Hartnett film "40 Days & 40 Nights" and it was pretty painful by the end.

during a period of enforced orgasm denial I think I made it to around 55-60 days and then I had a "wet dream".

Years. Before I discovered toys I couldn't make myself orgasm so there was really no point in doing it. I tried for a long time and just gave up.

I've never gone longer than a week. Even as a child I would do it.

Less than a week. I've never considered masturbation a problem, so when I didn't have a partner, I'd take care of things myself.