Good question. Almost every 'great' item I have owned has shown up in an auction within three years. I used to think it was because of buyer's remorse, but it's probably people just getting tired of an item after a while. I'm the same way - pieces I think I will never sell start getting stale after a year or two.
Last night I saw two of my former items in LOTG, including one that I said I would never sell, and the next owner said the same. I have no idea how many collectors owned it after him, but the entire process has taken three years