I had a smilar problem and surgery really helped - they opened up the sinus passageways to make them larger - even if you do get a bit of congestion, the passageways are wider so they shouldn't become blocked.
Medication will obvously help too, but it is the plumbing that will be causing the problems and you might find it is relatively easily fixed. Try to find a good ENT specialist (not your GP they will just prescribe Beconase)
Hufty