I know I've bought/rebought Space: 1999 several times: the two Sybil Danning "Adventure Video" releases (Alien Attack and Journey Through the Black Sun), then bootleg VHS (whole run), then one of the four single-episode VHS releases that never got further than that, then some of the Columbia House/re-TV 2-episode VHS tapes, then the PAL-format VHS (whole run, including the other two movies), then the OOP CBS/Fox VHS of Destination Moonbase Alpha, then A&E DVDs (whole run), and finally, Network blu-rays.
Only thing I didn't buy were the laserdiscs. Seeing a few of them at Camelot Music almost got me to take the plunge to buy a player (and the discs), but they didn't have them all, and since this was pre-internet, I wasn't too optimistic I'd be able to find the whole run, so didn't bother (this was before I knew that the episode made into movies weren't available on laser in the US anyway).