If you really need to read data from a 40 year old tape you must also store a computer able to read the tape. Most companies with large LTO archives migrate tape from generation to generation, sometimes skipping one. That is why LTO drives can read/write back one gen while they can only read 2 gens back. BUT LTO is the most common tape format by a LOT so it is pretty likely that even 40 years from today there will be drives that can read LTO7,8,9