I usually do this. When I feel that a model has gotten "old," I replace it and give the old one away. Usually my conversions, and usually because I think of a way to do it better.
I bought a trygon, a carnifex and a set of dragon wings to make a nid harpy. A few months back I gave it away because I figured out how to make one better.
And I occasionally give away unopened boxes that were purchased at a moment of weakness. Like that time I bought a GK terminator. Good model, but still three days later I looked at it and thought wtf...
Nonsense is our Salvation