What might be causing confusion is TTL, time-to-live, doesn't normally run against any real-time clock, it's usually just a limit on the number of "hops" a packet can make. Normally routers decrement the value by 1. When it reaches zero, the packet is no longer forwarded.
If there's a routing loop, this will eventually destroy the packet. It could happen very quickly on a LAN or take much, much longer on a low bandwidth but high latency WAN links.
As several people have pointed out there is not any limit on actual time that an IP packet can exist (there is no discard based on expiration of some timer). There are several reasons why there is no such expiration of a packet. One of the reasons is that we do not have any mechanism to accurately know when the packet was generated, so we can never know accurately how long the packet has existed, and therefore can never know precisely when the packet should expire.
TTL is as close as there is to what you are looking for.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...