When preparing for my first tour, two weeks across Easstern Canada, I got overconfident because I went so long without a puncture, and put on some nice light non-flat-resistant tires early in the season before the tour. Big Mistake -
SO! MANY! FLATS!
Day 1 x 1
Day 4 X 4
Day 6 X 2
A friend's wife was meeting us in a city along our route, and she brought a selection of my friend's used tires, so I swapped out my rear for a well worn tire with a flat resistant feature. This stopped the punctures for the most part,
Day 9 X 1
but a few days later, paranoid about how worn was the tire, I stopped in a shop and bought a new one of the same model (specialized 'Black Belt') and replaced the worn one. All great except for that, after the new tire was installed in the parking lot, we got turned around trying to find our route and wound up on the busy Trans-Canada highway, where I ran over a piece of sharp metal and punctured my brand new tire about 2km from the shop.
Day 10 X 1
Like OP, I had lots of practice fixing flats. I, too, was planning on relying on C2 cartridges, but I found this wasn't practical for long distance touring... you can't assume you're going to have a finite number of times you need to reinflate. Also, I found there is a small failure rate of CO2 inflators - sometimes a gasket isn't seated right or gets frozen by the CO2 and you don't get full inflation. A decent pump is a must.
I think the only reason my group didn't leave me by the side of the road after my 4th or 5th successive puncture was that, because I have so much flat fixing experience from working in shops, I was able to get back on the road in less than ~5 minutes each time, and they remarked that I was always still smiling and in a good mood. Otherwise they would have gotten sick of me real quick.