Re: A writeable CD left on window sill
Magnetic media seems to last quite well, even under less than ideal storage conditions.
Eg the games that went with the Spectrum I sold a year or two ago, including the home recorded "backups", loaded quite happily (mid 1980s)
Similarly the QL microdrive cartridges, the Atari 3.5" disks and the IBM PC XT 5 1/4" disks, as well as the 10 meg hard drive (late 80's).
Just stored in cardboard boxes in the (distinctly non temperature controlled) loft.