There is a good rule of thumb for keeping any kinds of file or resource. (Including real 3d items).
If you have so much kept for so long that you can not put your hands on it within a reasonably short amount of time it's best not to keep it.
And for people who mutter "search" or "indexing" I always ask whether they can actually identify a search item that would locate the file they need. If you can then it fits the criterion for retention anyway.
But it starts with - stuff that's worth keeping is worth filing*. Stuff that's not worth filing isn't worth keeping.
*Saving isn't filing
Biting the hand that feeds IT
