1. If you want to preserve digital files, upload them to the Internet Archive at Archive.org where they will be preserved permanently. The BBC Sound Archives rejects items more often than not, but Archive.org never rejects an upload. If they eventually have to take it off display, it will still exist in their storage somewhere.
2. If you want to preserve real items, e.g. video tapes, leave them as a gift in your Will. Donate them to Kaleidoscope now, or leave your entire collection as a bequest to the British Library in London, which accepts pretty much anything that can be catalogued. It has a large collection of, for example, old reel to reel audio tapes, donated over the past 25 years, and still has the equipment to digitise these tapes. The British Library actually stores physically a huge quantity of tapes donated by the BBC, when the old reels in the BBC Sound Archive were converted to digital formats. 'Library' should not be misunderstood as meaning only books - go take a look at the BL's online catalogue to get an idea of how broad the scope of their collections are.