How to change the timeout value to be greater than 99 seconds.
Open the SNMP Configuration panel. Select Help to find some information on the TIMEOUT field as well as changing the maximum value:
Read-write field. Enter a value indicating the amount of time (in seconds) that the management application will wait for a response before attempting to retry the request to the target node. Valid values include 0.1 to 99; the timeout value cannot be zero. If you need a larger maximum value, you can change the upper limit by increasing the value of the X11 resource xnmsnmpconf.maxTimeout.
If SNMP requests to all agents are timing out, increase the default timeout value. If SNMP requests to a specific agent are timing out, configure a different timeout value for that agent.