uh, where?I keep everything.
I use it.
I have sold, given, and traded away quite a bit of the collection. The rest, still lots of it, are books that I'll pack up but will still occasionally use. Most the of the third edition stuff I've kept I'll be able to easily use in 4ed or 1ed. Luckily, converting between editions has never been a problem.
I've always felt the same. The next module I'll be running with my 1st Edtiion group is a 3.5E Eberron one, which I'll be able to fit in two of the four sections with minimal modification*. Generally, I have found that books/modules from any edition can be used....stuff I've kept I'll be able to easily use in 4ed or 1ed. Luckily, converting between editions has never been a problem.