For me the limiting factors are space - I have a nice music room, but it can’t hold much more than 22 basses and 6 guitars, even with some in cases. Plus I often have a few instruments I’m repairing.
And not to be morbid, but having been an executor two times in the last couple of years, I am seriously starting to think about what my family will do with all my stuff when I kick the bucket.
Selling a few instruments is one thing, but assuming my daughter would keep a few, she would still be looking at selling 20 or so. That’s a fair bit of work!