Steam

i suspect a lot of these people are actually just experiencing the reason why we're constantly told to stay active and eat healthily..

It takes a couple of months/years on estrogen :3 Not guaranteed tho!

Early 30s, if it is getting no action whatsoever, I reckon.

Depends, I'm only 33, but my meds make it really fucking hard to be hard.

Well, there’s a period when you’re younger when it’s almost involuntary. Later, it’s just super easy all the time. Over time, it slowly becomes less easy, over the next few decades, sooner for some, later for others.

Many things can affect this. Blood pressure has a lot to do with. Also stress and other psychological and physiological factors. Talk to a urologist if you have concerns.