I air down and up again on average about 4 times a week, and I’m the impatient sort.
When I’m not in too much hurry, or not working in the blazing desert sun, I use a compressor. For the last 15 years or so, most often my Viair 450. I’ve also had a couple of twin ARB, and the inflation time is comparable; generally 10 minutes or so depending on how much pressure change is involved.
This year I’m using a compressor I bought at NAPA (unfortunately discontinued I hear). It draws 90 amps and has dual cylinders. It’s about a 5 minute or less job. It was an inexpensive chynese product, and I have noted some diminishing performance as the months go by. It’s clearly not going to last like the Viair, but for the performance I’d buy one every year if I can find one.
To the question at hand, when it’s hot, there’s no shade, and I’m tired and ready to hit the road I hook up my CO2 tank. Two minutes, maybe 90 seconds depending on how much I need. You don’t need the overpriced big name product either. I got the tank and regulator from a welding supply store.
Times above are to inflate all 4, not including time to break out the gear and hook it up. Typically 25-40 on 35” tires. I use a 4 hose spider I made to inflate all 4 simultaneously. Make that yourself too, no need for $$$ kits sold under various brands.
PS- a generic welding tank is identical to a powertank, except for the graphics. And you can exchange them at most shops, so certification is never a problem. Sometimes I get mine refilled; other times it’s exchanged.