This Integer32 (0 or 60..2147483647 seconds) is described as the number of seconds before the SA is completely deleted, after which a new phase-1 ISAKMP negotiation must occur; a value of 0 means this lifetime parameter is not sent to the remote peer in any proposal. An admin tunes this to control how often an active tunnel must fully renegotiate from scratch, trading off security freshness against the connection-interruption risk of frequent full renegotiations. For example, an admin running a latency-sensitive tunnel might raise this value so full renegotiations happen less often, while a security-conscious admin on a sensitive link would keep it low.