My first tour I was using some lightweight tires, which I swapped out mid tour because of the constant flats. I bought new flat-resistant tires at a bike shop and installed them in the parking lot.
I had my next flat tire about 2km away from the bike shop. This was also my final flat of the tour.
My buddy had installed brand new Marathon extremes for the tour and laughed at me every time I flatted
The morning of the last day of the tour we walk towards our bike and I pointed and laughed - he had a flat tire from a tack that worked its way through the tread.