Before I say goodbye to data forever, I make a winrar file of the folder. I monitor it, to see how much storage space I'm saving and if it's worth the bother, and it often is (not so much video that's already compressed) so instead of regaining all the space, the trade off is just regain some of it and have that compressed archive still around.
Most *data*, It's not a burden to keep a long time. It's just accepting that I need to stop hoarding video files, particularly things I've already watched. Do I really need every episode of Mash, Seinfeld, Miami Vice, Columbo, Lost, etc etc etc etc? Of course I do.

Then again, wait long enough to forget details of the shows, and then today watching them in HD on a large screen instead of SD on a smaller CRT TV, it is an enhanced experience.