This Unsigned32 object, in seconds, sets how long the tunnel stays connected to a secondary concentrator (with clients attached) before attempting to switch back to the primary, where zero means no limit and a small nonzero value forces an almost immediate switch back. An engineer tunes it to control how 'sticky' a failover to a backup concentrator is. For example, setting this to zero on a tunnel that flaps between concentrators would let it remain on whichever secondary concentrator it failed over to indefinitely, avoiding repeated switch-back attempts.