A read-only TimeInterval giving the elapsed time since the subscriber unit last lost synchronization with the remote end. This tells an admin how recently the last sync-loss event occurred, useful context alongside the cumulative failure count for judging whether a problem is ongoing or resolved. For example, a very small p2mpSuLastSyncFailTime combined with a recently incremented p2mpSuSyncFailureCount would tell the admin that a sync-loss event just happened moments ago, worth investigating immediately rather than treating as historical.