[GRC]

1. Put them in a box, put some silica gel in the box with them to absorb moisture, consider sealing the box to keep dust, dirt and moisture out, and label the box with a description of the contents.

2. Keep one working cassette deck.

In a few years, some brands of CDRs won't play back properly.
In a few years, some of your HDDs will/may have failed.

In a few years, you'll STILL be able to play the cassettes and make a nnew digital copy.

I've got 'reputable' brand CDRs that I recorded in 1998 that won't play back. I've had hard drives that were bought post-2000 fail on me.

ALL, or ALMOST ALL, of the reel-to-reel tapes and cassettes that I recorded in the 1970s STILL play back. They might have lost some high-end, there may be a drop out here and there, but they're essentially still playing back as they were in the 1970s.

Keep 'em, and keep 'em safe. You'll thank yourself for it one day.