This topic appears every so often - and I enjoy reading the answers every time.
Me: I keep loc boxes, accessory boxes and a few "special-to-me" car boxes. That's it! Storage is in the attic. We have a very moderate beach climate so no issues.
OH!! WAIT!! I forgot! I DO have a fairly extensive PostWar collection. ALL the P/W boxes that I have are saved and given special attention & treatment.