There is no time limit for just running on a SUB.
You need to get in touch with your SE/AM and see if they can provide the recovery disk as it's no longer available online as it's EOS/EOL.
Bear in mind that there is no guarantee the recovery disk will be able to fix the PUB, it's a best effort attempt, but it can fail to repair it and there is no other way besides a DRS restore.
I'd start looking into building a new system with a current version and how to get some info out to migrate it.
HTH
java
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