[G6Tanuki]

Replicate your copies - across different physical media (so have a BluRay, a DVD and a HDD copy)

Also remember the necessity for physical storage-diversity: don't store the different media together! Otherwise you risk both copies being wiped-out if your basement floods/house catches fire/mice build their nests in your storage. [I know someone who put a plastic storage-bin of VHS tapes in the attic: over the winter snow blew under the eaves and it was some months before he discovered his tapes unhappily sitting in half an inch of mould-encrusted water]

Give one copy to a friend, take it to your holiday-cottage/office or something.

Personally, I like 'cloud' backup with several different providers: that way if one goes bust there's still a fallback option.