Sealed 8-track tapes
Still in the original cellophane wrapping
Usually the tape quality is very good because no wear of playing it.
However never just put a "new" tapes in your player without replacing the splicing foil
At least check if the rubber roller is not desintegrated. If it is sticky definately keep the tape away from your player and 8-track collection to prevent sticky stuff getting all over the place.
Check if foampads are still "foamy" and not desintegrated, or in case of metal with Felt, check if felt is still there and strongly attached to the metal. An if the metal is not croocked. It should push the tape in a straight way onto the tape head.