Customers on the Ultimate package can adjust the frequency of checks performed on their account, via the Account -> Settings section of the RBLTracker portal:
You can adjust the frequency of checks from hourly (24 times per day), to every 48 hours (once every 2 days).
Take care when adjusting the check frequency value, as it may affect the overall cost for monitoring your hosts. There is a simple Cost Calculator available from the Billing -> Cost Calculator page of the portal to help with budgeting your RBLTracker account.