You use the SNMP_TIMER field in the SNMP tab to specify the time interval between the health-update packets that are emitted by the Screen. If you do not specify any Alert receivers, no health-update packets are issued.
If you set the SNMP_TIMER field is set to zero (or lesvr it empty) and there are Alert receivers, no health-update packets issued, although other SNMP alerts are sent to the Alert receivers.