Bedroom numbers in house?

[Newmum26]

We have a 3 bedroom house. We have one DS so far and plan to have one more child so In theory we would each have a bedroom each.
However our house is a Bungalow with a lot extension so the way our 3 bedrooms are set up is 2 downstairs and 1 upstairs with N en suite. The upstairs used to be mine and DH bedroom until DS went into his own room downstairs and we moved into the downstairs bedroom to be near him. It works well.
I'm now stressing about when we have another. What would you do? My thoughts are baby will be in with us for a while and lingers than 6 months if it suits. Then it would go into DS bedroom next to us to share until DS was old enough to go upstairs to the bedroom? I'm not sure what age this would be though 🤔
Has anyone got any similar experiences or set ups and how do you make it work?
Thanks!

I'd let them share until they are big enough to be downstairs alone then you go back upstairs.

My friend had similar set up and her dd was downstairs alone from being a tiny baby, which always felt weird.

I personally would want to stay on the ground floor, put one or both children in the upstairs room.