I have a deviated septum that was found when my allergy shots started working but I still couldn't breathe through my nose. I also have mild sinus issues with them clogging and a mild infection (normally my immune system gets it under control within a week or so).
I have the surgery in a couple of weeks so I can't comment on the long term affects yet but I'm hopeful it will help!
My son in law has severe allergies and has had surgery which helped but only lasted a year or two and they had to do it again. I would ask the doctor what the chances are of having to repeat this in the future. He also had a deviated septum and clogged sinus issues.