Generally sinusitis starts off as a common viral infection like common cold. This infection generally subsides within 5 to 7 days. During this time the nasal structures can swell and facilitate the stagnation of fluids in sinuses that leads to acute sinusitis which lasts from 6th day of the infection to 15th day. From the 15th day to 45th day of the infection comes the subacute stage followed by chronic stage. Whenever a chronic stage patient's immunity takes a hit the infection moves to "acute on sinusitis" stage and moves back to chronic when the immunity is up.
How long does it take to recover from a sinus infection?
Given this paragraph about Sinusitis, it takes 5-7 days to feel much better.