I came across the link below while reading an OP's question about EoL support for an older version of Backup Exec.
This will tell you how much longer you have support for on your particular version of Backup Exec. It starts at v.10 (older versions have long since been confined to support history), and it should be useful to you for reference purposes.
The link below relates to the EoL policy from Symantec:
The link below relates to the EoL FAQ as well...
Take a look, and bookmark them as it will help you decide when to move off your version onto a newer, supported version of BE.