analog

Medical note: Sustaining a single erection for more than 4 hours is unhealthy for the tissues in the penis. Blood only has so much oxygen in it, and with extended erections the blood in the penis isn't circulating back out, it's staying in there the whole time, which means the tissues will use up all available oxygen and begin to suffer. The lack of oxygen causes damage to erectile tissues and the formation of scar tissue- and can eventually lead to a permanent loss of function. Note that this is for a single, sustained erection- if you have an erection for 2 hours, then lose it, then form another erection, the clock pretty much resets with the new erection. The reason for this is newly oxygenated blood has flowed inside the penis to supply the tissues again.

As for the topic, the "recharge" period is different for everyone. It can be instant, take 5 - 20 minutes, or even an hour or more. I believe most fall in a 5 - 30 minute range, but longer isn't necessarily unheard of. If it's more than an hour or two, talk to your doctor to be sure there isn't another factor that is causing the delay. Psychological arousal can also play a role in the recharge period.

Some men find that after starting a relationship, their recharge time decreases. I know that for myself, the recharge time can be up to 10 minutes at first, but goes to almost zero once i've been with a girl for a little while. Psychology plays a substantial role, even in males, in sexual arousal.