Sleep amount depends entirely upon Daily Activity Levels or planned levels. I have no preset minimum/maximum amount for sleep.
When I was a truck driver under the old logbook rules, I slept or napped as I needed which often interrupted my Circadian Rhythm. The new rules are like punching a clock as sleep patterns usually develop.
I seem to get 6-8 hours yet counting the wake up periods, probably sleep 5-7 hours. These (and other) factors play in too: Neighbors, Noises, Timely Shutting Off Electronics before sleeping, Worry, Stress, Body Pains, Pets.....