30 year old tapes
It depends on the binder used on the oxide and the storage conditions. In the pre-cassette Reel to Reel era they produced a rubbish formulation. Earlier and later tapes are OK.
With actual computer "tape backups", some tapes of entry level floppy interface drives could be unreadable a week later, or other tapes could be OK years later depending on maintenance of drive, atmosphere at the computer, make of tape and the tape storage.
Biting the hand that feeds IT
