Which watch for all day plus sleep tracking - eviltoast

I am getting more into sleep health and want to better understand my sleep habits so I have been looking at the Apple Watch.

If I spend the money on an Apple Watch I want to also be able to use it all day but I am realistic in that I know it has to be charged too.

I am leaning towards the series 9 but see that it is good for about 18 hours and then needs about 1.5 to get a full charge.

What are your routines to use your watch all day but also be able to get good sleep data?

TIA