My experiece with a severely damaged sinus occurred as result of a block occurring during a high altitude flight. When you run out of gas, you have to come down, so I did not have the luxury of skipping the dive so to speak. It took about a month to heal.
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One thing people don't often realize is that pressure differentials in sinuses that are too smal to cause pain, can cause a great deal of inflamation over the course of the dive and can cause a blockage later. One way to avoid that when you are on the edge in terms of sinus issues is to clear often and clear on the bottom whether you feel the need to or not to ensure that you are fully equalized. That will help devleoping a block or reverse block during the dive or shortly after the dive.
