if you mean the generic backend(a place to store secrets), they do not last a fixed amount of time, they are there forever.. there is a TTL, but vault does not erase anything that outlives it's TTL. Locally we just touch the TTL whenever we access it, in case someday the TTL's are followed and secrets get erased.

TOKENS however do get killed at the end of their TTL. But you can renew tokens forever if you allow for that.