Still, perhaps you could put it more under the player's control which items are removed. For example, you might make entry to a dungeon cost a sacrifice of 5 junk items per player per entry?
Thank you for your sincere opinions. Now I can see a pattern here:
As a player I don't think I would much like a random outbreak of "pests" to devour the whole of my collection.
Having one's collection limited or vulnerable isn't much fun.
You people are totally right. Flushing the player's special collection through the sinkhole is not a good idea at all, that will unlink the player from the game. But the basic idea is simply to remove items from the economy system, in order to avoid inflation. To keep this mechanic, players could mark all of their favorite items as part of their precious collection. That is a set of items of any size that they won't ever sell or exchange, and will receive constant care ensuring that no pest reaches it.
I've also seen pets and evolving/living items which need to be fed other items.