I keep hold of a lot of stuff because it could come in handy or be worth a few ££,
Then it comes a time I either give it away, or take it to the skip cos I can't be f**ked adveryising it and having all sorts show up to haggle over something for a fiver, all the time eyeing up what else I have lying around.
Sure enough tho, a few weeks later, you start cobbling something together in the shed, say 'I've got that somewhere', go and look for it then remember you skipped it!!
Like Paulus said, the other problem is knowing you've got it.....somewhere, but trying to find it is another matter