There are several different CO-2 inflators and some seem to have better O rings than others. Some also have triggers that allow slower inflation. I have a friend that has one that seems to hold C0-2 for at least one or two days. I have an Air Chuck ands once puncture the C0-2 it is pretty much done.

In an unrelated story I have had a CO-2 that was still intact and once punctured it turned out to be empty. I had another cartrage but thank goodness I had a pump as well.