I take Melatonin every 2 nights (3 mg, was 5 mg) but it doesn't always work. Last night for example I woke about 0400, after going to sleep about 2230-2300.
In the early days I slept longer (as I believe research has shown), but now my 'ideal' seems to be about 7-8 hrs. I have very rarely been able to get any sleep during the day, at home anyway - maybe I did in hospital? (because couldn't access any of my usual activities)
It seems to vary with what I take (and possibly what I eat); for example last night I took a cetirizine tablet with little effect, and on previous nights I haven't had enough sleep with chlorphenamine, although sometimes I do.
I am going to have one or probably two promethazine tablets tonight, which usually works.