Are you sure it is keeping your Pool condition setting? We have this issue with our 9.08 install, the media pools cannot be changed from the default 36 month Condition setting so any tapes that were formatted 3 years ago will fail if placed in a pool like this. Some of our pools are respecting the settings I want and the tapes will be fine.
I've started just reformatting tapes that expire and are marked poor to reset this condition.
I opened a support case and was told it wasn't production impacting so they refused to open a backline case to get a fix created.
I'm hoping they fixed it with the 9.08_113 patches but my 2nd CM had errors during upgrades that prevents tape drives from working so I can't upgrade until that is resolved with support.