Flats come in bunches. I went through a month where I probably got 8 flats. Then recently, none for the past four weeks or so (I have been averaging over 300 miles weekly all through July/August).

Then sometimes there's a persistent cause you are missing. Could be a rough spot on your rim strip. Could be a microscopic piece of glass or wire that you failed to locate and extract from the tire casing after a recent puncture (they can be hard to locate and find, sometimes you have to look in small cuts in the tread and dig them out). For me it sometimes tends to be tires that may not look so bad at first glance, but they are really worn. Worn out tires create flats several ways: small cuts in the sidewall and casing that abrade inner tubes, and more pinch flat because the kevlar tire beads are old and limp and don't seat as predictably when you mount a new tube. This latter phenomena is greatly exacerbated if you ride deep dish carbon wheels (anything from 38 mm and deeper).

When in doubt replace the tire. After that replace the rim strip. If all that fails, consider it a perfect excuse to buy new Zipps.