Hello,
To assist you in determining the bad tapes, look into Networker logs for 
media errors, you can also look at the tape library for it's own logs and 
errors to remove any bad media ( errors may be specific per tape vendor).
I also have the operations staff visually inspect all tapes going into 
library for any leader, physical damage etc , as it often happens that 
once a bad LTO tape gets into the drive , then it's a service call and the 
tech usually have to pull out the drive unload the tape, not a good 
scenario, especially, if you run backups, test etc 24X7.
Then it's also the problem of windows re-sequiencing the drives ( only 
speaking of Windows) if an firmware  is updated on the tape driver or a 
new tape drive with different firmware is added to the mix then windows 
tends to leave the drive without drivers loaded ( now you got drive 
re-sequincing), this has happed to me so i just wanted to raise the flag( 
There are workarounds, newer, IBM drivers has ability to persistently bind 
the tape address, Adic offers Auto Leveling of Firmware, etc).
Sometime the errors are just caused due to lack of drive cleaning so 
follow the Tape manufacturers directions on how often the cleaning should 
be done.
Lastly, mminfo would be able to tell which tapes have  had maximum number 
of mounts, you could chose to retire most used media at some point.
Thanks

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