Admitted hoarder here. I have three complete bikes and a project. They each use parts that are completely different from each other (four different wheel sizes, three totally different shifter sets, at least three different gearing arrangements). In addition to my completed bikes, I've generally got enough parts to build another complete bike of some sort. I've gotten better about it recently, selling a lot of my spare parts- but selling on ebay means I peek over at the auctions from time to time. I keep rolling the money I make off of a few small part into funds for a nicer thing that I again sell to roll into something else....