The only thing I've ever "collected" was music - first LP's and then CD's.
I ran a store from '79 to'87 and ended up with about 3200 LP's and probably 300 CD's.
Over the next 10 years I sold off my record collection at local shows down to about 350 and upped my CD collection to about 900.
I also have about 1000 titles on CDR's recorded from various sources (local library) and probably 3-4000 titles on very high quality cassettes from the record store days......I had/still have a few great decks and the quality on these recording are really good.
I look at it all and think it's overkill sometimes, but market value-wise it's not that much. I still think about selling the turntable and vinyl (probably get me 700 at best) but for now that's my "collection" status! They are all stored "properly" so access is a cinch and I can enjoy them on demand.
When everything you own fits in less than 400 sq ft, you learn to prioritize pretty quickly!