I can still manage stairs - just more slowly now - but I would like my own sleeping quarters - I have been told that I sometimes snore - very loudly - and not even my spouse is "good" with that at times.
So good sound-proofing between the bedroom walls would be a good thing.
Also - an easily accessible public restroom on each floor - I don't want to have to go two blocks and three flights of stairs to answer nature's call!