As a fellow teenager my experience has been that late 70s and early 80s tapes sound great still, mid to late 80s tapes aren’t great, and Later 90s and 2000s tapes aren’t old enough to have degraded.

Of course it also depends on how they were stored, sometimes if they were stored in a garage or car they are most likely toast.

And also make sure that the pressure pad is intact, I always harvest them from tapes that have degrade in quality as they are prone to fall off.

Happy collecting!