Also, with so much tape to play, a hefty supply of cotton buds to clean tape heads, capstans, rollers, tape guides.
Oxide will always degrade over time, and shed it's valuable information all over your tape machine!
So, cut down the replays as much as possible.
If it's any cosolation I've got a few tapes recorded in the 1950's which still play as good as new.
If all else fails, transfer them to 78's! I've got some from the early 1900's....Maybe the folks back then knew something that we don't!

Good Luck again Ralph Jordan.