DNS check every 2 min, it takes 30 minutes for a device to go green after the ip address has changed

InterMapper's timer for updating each device's DNS is tied to the TTL of the associated DNS record on your DNS server (min. 2 minutes, max 24 hours).

If the TTL is low enough, reprobing the device or using a sub-minute poll interval can make the DNS update appear nearly instantaneous.

Check the time-to-live setting on your DNS servers, and see whether that matches the update period you're seeing?