How long do CO2 pellet guns last?

It varies greatly. There's nothing inherently difficult about keeping CO2 contained compared to keeping air in a PCP. The one difference I would note is that CO2 guns typically occupy the bottom end of the price spectrum so poor quality O-rings and nicked O-rings are a common problem. So there's a good chance you may have to swap the OEM O-rings in short order but if you use decent quality replacements and take care not to let them get cut on installation, they will last for years.
 
It varies greatly.


Yup.Depends upon the CO2 system too, at least in terms of maint/repair . 12gram Carts? 90Gram bottles? Bulk fill 4/9/12/20 ounce bottle? The larger ones are easy to maintain in a week or decade on the bottle/connection end. Rest of the gun depends. Bottles are mostly common paintball fittings/seals. CO2 carts sealling to pistol inserts or internal to QB/Crosman tube like stuff is a little tougher, and I've never done it. Although I do have at least one that needs this kinds of work.



None of these guns, regardless of powerplant, are repair/maint free..... Could be weeks, could be many years...,


 
The oldest Co2 gun I currently own is a Crosman 112 I've 'personalized' because they're such incredible airguns. They were produced from 1949 through 1953 or 54. While refinishing it in DuraCoat about 15 years ago I replaced all the seals, and she still holds a charge for months at a time. As to how long a Co2 gun lasts, considering this one is at least 65 years old, now looks better than new, and outshoots any Co2 pistol produced in 2019, I'd guess a good Co2 gun can last 2 or 3 human life-times.

1560391903_17370701275d01b0dfc27174.49076399_112 Manlicher custom.JPG


BTW, to any little-red-ballers waiting for an excuse to cast anonymous aspersion to the effect of "untrue", "inaccurate", or "hot air n gasman", feel free to do so IF you can show me a currently-produced .22 Co2 pistol that can average .58" center-to-center groups at 25 yards, produce over 500 FPS and 8 foot-pounds of muzzle energy, and last multiple lifetimes. I don't make fantastic claims without proof... ever. Just because a little-baller doesn't want to believe something 'he' isn't capable of, doesn't make it any less true. 

Heres a .177 version Model 111 I also personalized. It broke 550 FPS, 6 foot-pounds, and averaged .69" c-t-c 25 yard groups.

1560393082_18953046645d01b57a466885.82289203_Custom 111 FL.jpg





 
The oldest Co2 gun I currently own is a Crosman 112 I've 'personalized' because they're such incredible airguns. They were produced from 1949 through 1953 or 54. While refinishing it in DuraCoat about 15 years ago I replaced all the seals, and she still holds a charge for months at a time. As to how long a Co2 gun lasts, considering this one is at least 65 years old, now looks better than new, and outshoots any Co2 pistol produced in 2019, I'd guess a good Co2 gun can last 2 or 3 human life-times.

1560391903_17370701275d01b0dfc27174.49076399_112 Manlicher custom.JPG


BTW, to any little-red-ballers waiting for an excuse to cast anonymous aspersion to the effect of "untrue", "inaccurate", or "hot air n gasman", feel free to do so IF you can show me a currently-produced .22 Co2 pistol that can average .58" center-to-center groups at 25 yards, produce over 500 FPS and 8 foot-pounds of muzzle energy, and last multiple lifetimes. I don't make fantastic claims without proof... ever. Just because a little-baller doesn't want to believe something 'he' isn't capable of, doesn't make it any less true. 

Heres a .177 version Model 111 I also personalized. It broke 550 FPS, 6 foot-pounds, and averaged .69" c-t-c 25 yard groups.

1560393082_18953046645d01b57a466885.82289203_Custom 111 FL.jpg




Neat old air guns.


 
....they last longer if we put a drop of oil on the nose of every other cartridge , and keep at least SOME pressure in our co2 guns, it could last 20 tears. benjamin's and sheridans last 15-20 yrs... same reason we leave a few pumps in our pumpers, and some pressure when storing pcp/hpa guns . ... but , usually when the hard rubber/plastic seal that seals around the co2 nose when punctured - that special rubber washer that we find on ebay to fix the top nose end of our 2240/2260 valves , where the co2 seats and get poked.... that's when they usually call me.....especially with the bb pistol replicas that look like a real gun (and no fun to take apart - or put together) ....it a $5-10 part , but takes some assembley and re-assembly of your co2 rig. i had one rebuilt benjamin 257 (.177) pocket rocket pistol that i test fired about every week (that thing was cool) - had the box, papers, everything like it was in 1953......and it was an 8 gr short co2 cart .....but held air for about 5 months.... - paul.
 
Thats like saying how long will I live. Well we all hope maybe 100 years but if we smoke, drink, and go to the disco every weekend we may die of aids at 35.same with your co2 if you dont start with good seals and use pellgun oil every cartridge or every other co2 cartridge then your gun will develop full blown aids. Take care of yourselves and for gods sake quit taking your co2 guns to the disco!