Gregory's Server@polychrome @atomicpoet @anji it's true - you cannot trust anyone who's motives are not preservation to preserve your media. Archiving has been getting increasingly difficult and expensive over the years as the volume and diversity of media goes up, and it's expensive.
I'd go one further and say optical media - not necessarily CD/DVD, though - is the way to go - formed by irreversible chemical/ mechanical processes. Tapes and disks are fine - but are erasable and so less durable.
@polychrome @atomicpoet @anji also - tape heads have a finite lifetime (in hours read). Many kinds of tape machines (and this heads) which were once common are no longer manufactured: thus there is a finite supply of tape heads. There are archives in the world which have more hours of media stored in them than there are tape head hours in the world. So some of the archive is already lost - it's just we have to decide which bit we don't recover.