For now in Template Module Generic SNMP for uptime used OID 1.3.6.1.2.1.1.3.0 which in fact is a 32-bit counter and will roll over after 496 days.

Also since for value hundred of seconds used - preproc step with Custom multiplayer used.

But you can poll 1.3.6.1.6.3.10.2.1.3.0 which returns the uptime in seconds and should not roll over for 135 years. And also since value returns in seconds preproc steps can be deleted.