How long R-22 lasts depends on whether you mean in a sealed air conditioning system or in the atmosphere, two very different time scales. In a properly sealed, leak-free air conditioning system, R-22 does not get used up, it recirculates through compression, condensation, expansion, and evaporation continuously, so it should last for the life of the equipment, typically 15 to 20 years, without needing replacement unless there is a leak. If there is a leak, it will leak out in weeks to months depending on leak size. In the atmosphere, R-22 has an atmospheric lifetime of about 12 years, meaning it takes about 12 years for most of it to be broken down by chemical reactions, primarily in the troposphere and stratosphere. During that time, it contributes to ozone depletion because it contains chlorine and has ozone depletion potential of 0.05, and it acts as a greenhouse gas with global warming potential around 1810 over 100 years. So in equipment it lasts indefinitely if contained, but once released it persists for about a decade before being destroyed, which is why recovery rather than venting is legally required and why its production was banned.
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