I have almost 2,000 Build/Buy items alone and I keep putting it off. Like, I'll... organize this later. But I keep downloading new custom lots that require *new* CC (because I absolutely refuse to buy all the stuff packs).
My other downloads are organized into 25 super specific folders. So, for example, there's a folder called "Shoes, Male" and "Shoes, Female." And in the "Shoes, Female" folder, there's more folders called "Heels", "Boots", etc. So that, if one of my girl's shoes start acting up, I only have to go through 50 files instead of 100+ files in a general Shoe folder.
But for Build/Buy stuff I literally just have one folder called "Objects." I don't know how I ended up getting 2,000 items in that folder, because I don't even build things and rarely do I have the patience to decorate someone's room.