Eight hours is my ideal, usually get less. One change with ageing is that my sleep has been less reliable - I used to count myself as someone without sleep issues, but no more. Re waking up and (not) feeling refreshed, even after long sleep, has anyone noticed truth in the sleep cycles idea (roughly 90 mins, wake up in the middleand feel awful)? Only explanation I have for the randomness of feeling good in the mornings.
Blue light and information overload is evil. I always feel better if I put down the screens at, say, 8pm, but rarely happens
Siestas can be wonderful. Britain, US etc are barbaric in enforced work hours