Flats can sometimes be a tricky thing to gauge. I tend to get more flats around April - June and then the occasional ones (sometimes) afterwards. Part of it is due to the debris that builds up over the winter that has yet to be cleaned up. Part of the problem was also me not paying attention to what's right on the road in front of me or cleaning off the tire after my commute (picking off glass shards or other debris which could work itself through). I've also noticed that my tires don't seem to collect as much debris now then they did when they were new.

I like my tires and only remember paying $20 at a LBS if memory serves me correctly. I might take a look at what Mad Scientist suggested once mine wear out.