Question about litter box

Hello everyone!!
Stormy is only 6 1/2 weeks old and so far no accidents since she came home on Saturday. She has two levels of the house she is able to be on. The first floor and the second floor. She can not get to the basement or the attic. I have a litter box in the bathroom on the second floor and one on the first floor in our dining room....At night she has been sleeping part of the night in our bed and part in the bathroom. She has not made any effort to go up and down the stairs until today. She goes up and down very well now that shes worked on it all day.
My question is......should I leave a litter box on each floor or should she be able to get to one left on the first or second floor already?
2nd question.......if we have a litter box in the bathroom on the second floor should she be expected to be able to get to it if shes in another room other than the bathroom when she goes to sleep.(with doors open of course)??

I want her to be able to go wherever but Im not sure if thats such a smart move at her age. AGain shes gone to the litter boxes ALL the time and doesnt appear to give me reason to worry but I dont want to expect more than what she can give ya know?? During the day we are home all day and I know shes OK going everywhere but at night Im unsure if she would be OK. I know Ill only find out by trial and error but Im hoping some of you can give me some of that wonderful insight you all have.
Thanks so much

Yes, leave the boxes.
Remember potty training your kids?
Takes a while before those muscles are strong enough to stray too far from the bathroom without an accident.

It's the same with baby kitties.

Thanks Arlyn
Thats what I figured but I just wanted to make sure. .....part of me was afraid that with leaving two boxes that she would never be able to go down to one, but I also knew shes still a kitten and for some reason I think Ive heard that for each floor have a litter box????
Anyhow thanks for responding so quickly.