Again, the bigger the boat the better the liveaboard experience is.
I think that the size of the boat, like most everything aboard, is a compromise. Sure, there's comfort with bigger size, but there's also a loss of access (fixed bridge clearance, protected anchorages, maneuverability, simplicity ...)
In our twenties we lived aboard a 30' boat that had headroom five inches less than my height,- I didn't suffer.
In our thirties we lived aboard a 33' boat with two children up to ages 7 & 9 in, pretty much, one cabin,- I didn't suffer.
In our forties we lived aboard a 41' boat with teenagers sharing the aft cabin.- I didn't suffer.
In our fifties our children moved away and we shopped for a smaller boat, but we could not find anything better that what we had paid off, -no suffering!
In our sixties we kept the same boat that I know well and we've replaced the engine, sails, rigging, electronics,- we're doing well.
In our seventies we will likely still be cruising, but if physical conditions move us off the boat, and that will happen eventually, we'll be doing well.
I have a 22 year old nephew who is living on a 22' Catilaina,- he's not suffering!