Re: Long term problem
how does one ensure that the Software is also still capable....
Use old Unix (BSD) tar to write to the tapes. Not Star or gtar, or any other newfangled tar. The original one.
Choose a blocking factor and stick to it. The "default" setting is not very portable over time (used to be 20 card images of 80 characters, now mostly 20 of 512 byte blocks).
Set the Block Size to variable, because fixed block sizes appear not very portable at all with different manufacturers: does 512 mean blocks of 512 bytes or 512 blocks of 512 bytes or 4k bytes, or something else? (depends which day of the week it is, mostly).
Use open source software, and save a copy of the source where you can find it. (probably not on an 8" floppy).