I guess it depends on your level of commitment... I go wheeling maybe a total of 20 days per year on a good year, and many of those outings are multi-day events where I don't bother airing up until it's time to head back home. I have seen CO2 tanks at work, even used one kindly lent to me to make quick work of a plugged flat on a trail once instead of pulling out my compressor, and they are pretty awesome.
However, it does take a level of commitment to have a scuba diving-sized tank installed on a bracket somewhere in your trunk 24/7 (you could leave it home when you are not wheeling I guess, but then you'd feel like an idiot if you needed it on your way to work one day and were forced to call AAA instead...) So far I have stuck to my cheapo MasterFlow MV-1050, for 60/70 bucks it does the job just fine - although much more slowly than a CO2 tank and of more high-end portable compressor such as the Viairs. I've been wheeling more or less regularly for 6-7 years now, and I've only blown through one unit so far (and a fair number of 30 amp fuses that sometimes blow when I run it for too long, but fuses are cheap and I have a pouch full of them in the compressor bag.) For a $120/130 total investment, I am still way ahead of the game compared to higher end compressors and Power tanks. And I have found I can stash it in the crawl space between second and lowered third row of seats of my LR4, along with my ARB flat tire repair kit, pressure gauge and Staun deflators, so it's always with me but out of sight when I don't need it.