Omani carriers frequently run "Double Credit" or "Extra Data" promotions, especially around holidays like Eid al-Fitr, Eid al-Adha, and Oman National Day. Waiting for these windows to perform a large top-up can significantly increase your usage time for the same cost.
Often, a promotion will give you "Bonus Credit." It is important to note that bonus credit usually expires much faster than your main balance (often within 3 to 7 days) and may only be valid for local calls, not international ones. Monitoring the official SMS notifications from Omantel or Ooredoo is the most reliable way to catch these 48-hour windows.