I do it so infrequently that I'm not all that good at it. 10 minutes. I only do it once a year or so. I'm just changing tubes.

I don't think CO2 would make it very much faster, because it only takes me about 2 minutes to pump up. Most of the time is spend horsing with the thing, getting stuff out, finding all the crap I dropped in the grass, stuffing it all back in one of my bags.