I've never passed more than 250 stones at a time. Probably have passed about 800 total. Two of my flushes had less than 5 stones. I HAVE seen a noticable improvement in my allergies, but it is no where near being a complete disappearance of them. But supposedly I have 1200 stones to go before that happens.
One thing to think about is allergies and sinusitis often occur together. Make sure you don't have an infection that is contributing to your misery. I used to have terrible sinusitis that my doctor blew off as "just allergies" When I finally got to the ENT, he was horrified at the state of my sinuses.