I don't really know, last I counted some years ago I had 4,200 physical CDs, probably around 5,000 now (that's the 'official' stuff -- lots of CDrs of concerts from trading groups back in the day, too). And now a little more than a terabyte it mostly FLAC (also some other lossless formats; maybe about 20 songs on mp3). It's actually too much to get to, and always more coming in. But for some of us this collecting thing is partially about BEING a library for all my friends. I just have a habit of doing family trees, or genealogies, of groupings of musicians. For jazz in particular that gets you very far afield from whatever the "seed" record is. For a certain temperament of collector who will go, for one example, from an Art Blakey record to Nancarrow or Ligeti, on the one hand, and to various rock musicians on the other, covering every degree of separation in between.. well, you can go crazy collecting.