The Catridge life time length is depends on the usuage of the tapes ie.,
1. More the time mounting the tapes & using regularly for backup/restore jobs
2. Depends on the maintainenace the tape drive in good condition Regularly, if not tapes get stuck in the drive often & which damages the tapes sometime.
For your query.
The data inside the tape depends on the retention period of backups. If it is retention level 9 Inifinty) the data is kep forever.
The Hardware vendor gives the warranty , if the tape is having any media write error or such kind of defect inside the tape & not for the data inside the tape.
If you feel the data is very much critical & needs in a high priority, u can perform a duplication of the images inside this tape. So that if one media is having any issue in read/write operation. you can still make use of the duplicate media for the restore action.