Al made a comment about looking for Wright Line tape seals. A story of mine: In the 90's I got to spend a lot of time sitting in tape libraries filled with tens of thousands of tapes hanging on racks from the hook on the tape seal. During a typical stretch (say 8 hours nominal) one or two tape seals would break and the tape would get dumped to the floor. Sometimes the seal would break in response to some kind of vibration in the room (after all, there were several tape drives getting loaded/unloaded etc. as well as me rummaging through the racks looking for tapes) but other times they seemed to break with absolutely no reason. Sometimes the black plastic hanger would break but more typically the white plastic seal would break near the hanger. I'd say from this that out of a library of 30,000 tapes with several tape seals breaking every day, that the expected MTBF of those Wright-line tape seal is probably 30 years. That's not necessarily the same as lifetime. As the plasticizers dry out I'd expect them to break more often. Sunlight and ozone+ heat can really do a doozy on plastics. The hard-plastic IBM tape seals seemed to be very much more vulnerable to breaking in transport than the Wright lines, and they'd also occasionally fail just hanging there on the tape rack, but I'm reluctant to make any statistical statements about them because so many were obviously broken in transport.