I need a lot more than that. Though as a teenager I happily burnt the candle at both ends and probably got rather less than 5 hours sleep a night, since being seriously ill I need far more sleep than the average healthy person.
I need more sleep than that. I used to get by on 5.5 hours sleep a night when my first born was young. I would have a nap on the train to and from work because it wasn't enough for me really. These days I get 7 to 8 hours sleep a night which is much better.
8+ hours' is what I've always needed to remain alert at work.
Now, can just sleep for as long as needed, for my health.
I'm an 'owl' & go to bed anywhere between 10.30pm to 5.30am! So sleep min 8 hours from whenever!