I used to just CO2 until patching a tire and reflatting took 4 carts. Ran out. Would have been nice to have a pump to check for punctures. Now my pump goes in my Camelback. Though if I go tubeless, I may change my mind.

Yes, buy the BB gun carts. They are much cheaper. Even if they are smaller, for the price you can use 2 and still come out ahead $$$.