I'm in my mid-forties now, and I've been doing it since my mid-twenties, so it is for awhile. I doubt I'll still be doing it in my mid-fifties ;-)
Parent with two young kids here.
I find it's quality over quantity. A sound 4-5 hours is far preferable to a broken 7-8 hours.
It depends on your genome
It does, but at least for me, the ritual requires a bit more work than that. My whole family is good with less than 8 hours of sleep and interestingly, growing up it was seen as a symptom of a problem if we slept for 8 or more hours. I am usually good with 5 or 6 hours of sleep a night, but in order to maintain that, I must ensure that I don't oversleep on the weekends, or my whatever thing gets out of whack and my body wants to oversleep on other days. I've also got to maintain my exercise regime, because for some reason, when I work out, I feel good and totally refreshed after 5-6 hours of sleep. But if I haven't worked out for a few days, or I overslept on the weekend, it takes me a week and some exercise to get back into feeling refreshed after only 5-6 hours of sleep.
5 or 6er here. Sleeping 12-14 on the weekends helps.