When thinning down the collection, what to keep and why?

[John Dallman]

Reasons to keep stuff:

• I might use it.
• It provides additional ideas for something I might use.
• It's fun to read.

For example, I have a large number of WWII games, none of which I expect to run, but which provide ideas for the long-running GURPS WWII game. Those that don't seem to have useful ideas are at risk of being given away, or discarded.