Yeah, but if worse comes to worst, the data is still the most likely to exist on the tape, and you should always be able to find some way to read the data off.

If you want to be super paranoid, save it on as many different types of media as possible. Each has its own strengths and weaknesses. For example, a flash drive might survive a flood that magnetic tape might not. And instead of just saving individual files, save files plus error correction files, using something like parchive2.

Also, as Matthew says, verify the data occasionally. If you don't know that one of the copies has gone bad, you don't know that all of them have gone bad.

And don't rely on non-open software. It might be hard in fifteen years to find the right tape drive, but it's going to be even harder to figure out how to read that undocumented file format.