Time to hold socket in state FIN-WAIT-2, if it was closed by our side. Peer can be broken and never close its side, or even die unexpectedly. The default value is 60 seconds.
Usual value used in 2.2 was 180 seconds, you may restore it, but remember that if your machine is even underloaded web server, you risk to overflow memory with lots of dead sockets. FIN-WAIT-2 sockets are less dangerous than FIN-WAIT-1, because they eat maximum 1.5 kilobytes of memory, but they tend to live longer.
See also: tcp_max_orphans.