30+ years after I stopped actively collecting, all I was left with was keys (and my Centaurs).
For the last 10 years (or so) of my collecting I was trading all my gold runs (and hot new stuff - new xmen, spider 252, etc.) for the keys I was looking for.
So I kind of traded my entire collection over a period of time for several keys (bat 1, sup 1, mf 52, flash 1, etc.).
I've scoffed stuff here and there since then (that I don't really consider part of my personal collection), and some things never got traded for keys (more fun 54, 55, action 4, sup 4, tec 5, etc. ).