Between the ages of 16- 25 I could easily get away with just 4/5hours sleep a night.
From 25 onwards it’s ramped up to a minimum of 6 and preferably 7/8 hours a night. I now thankfully have a good sleep pattern and seldom suffer from insomnia (maybe 1/2 a month). However I have had episodes of poor sleep lasting anywhere between several days to week/s due to stress (primarily work) which is now the biggest contributor to poor/lack of sleep.
It’s taken me sometime to admit it to myself but it’s surprising how much stress, once you identify and accept it, impacts your life.