when you can't keep their litter trays clean and their food bowls full
smelly catpoop and whingy cats = too many for the care level
Discussion
...so like 40ish?
i'd say 1 cat per square yard of floor area is the limit yeah... they don't pile on top of each other either, nor want to play all day long
also if they aren't all neutered it's gonna double up every 4 months at least, if not triple