Just started using these Co2 cartridges this year as I got tired of cranking the mini to pump up 120 lbs. However, it seems that after I've inflated a tire with C02, it goes substantially flat over 2 to 3 days. I'm used to topping off my tires each time I ride, but this pressure loss is substantially more. I haven't meticuously tracked pressure loss each time I've used a co2, it's more just an observation.
For example, the last time I rode, I flatted. I changed the tire and inflated with a c02 cartridge. No problems, I rode for another 2 hours. A couple days later I find some time to ride, but the same tire is flat. So I change the tire and check the tube for the leak but there is no leak. I also check the inside of the tire, it's fine. I also check the wheel itself, nothing obvious and the liner looks ok. Then I remember that I inflated with CO2. So, I put the old tube back in and inflate with a floor pump and the tire is rock solid the next day. Hmmmm.