You can quite easily check this for yourself: dig up some old school papers, the earlier the better. Then get some old books you have. I expect all of them to still be totally fine.

In my experience:

• Paper, ink and toner will probably last for centuries. Just keep them dry! And keeping another backup in another place doesn't hurt of course.
• CDRs, electronics and thermal printing on the other hand expire. I expect all of it to be useless within a few years up to a few decades.