I like to archive shows I enjoy a good bit though personally, and I get OCD about keeping any and every old OVA even if they suck or not, since those are the harder ones to find off and on. Lately though I often find myself redownloading better releases of older shows, whether it's an upgrade from VHS rips to DVD rips, or just a better group... it's been happening a lot lately, lol. Not that I'm complaining, a good excuse for me to rewatch that stuff.
The timing on it is always funny though. I watch Votoms, few months later GP releases super HQ releases of it. Same deal with Tekkeman Blade. Then Kimagure Orange Road. etc etc etc, lol.