With IPHost Network Monitor you can run simple snmp requests against a Cisco device in your network.
natAddrBindMaxIdleTime
nat Addr Bind Max Idle Time
1.3.6.1.2.1.123.1.6.1.10
This object indicates the maximum time for which this bind can be idle with no sessions attached to it. The value of this object is of relevance only for dynamic NAT.
Back to NAT-MIB MIB page.
IPHost Network monitor allows you to monitor natAddrBindMaxIdleTime on Cisco device via the SNMP protocol. Download IPHost Network Monitor (500 monitors for 30 days, 50 monitors free forever) to start monitoring Cisco firewalls right now.