This INTEGER, ranging 1 to 10000, sets how long, presumably in seconds, a RIP route is kept before it ages out if not refreshed. A shorter age time makes the virtual router drop stale routes faster after a neighbor stops advertising them, at the cost of being more sensitive to brief update loss. An admin operating RIP over an unreliable link would raise this value so a single missed update does not prematurely age out an otherwise valid route.