This is why it is understandable that some users might keep their devices around longer as it is too costly to upgrade, but exactly how long do they keep them around for? We suppose that ranges from consumer to consumer, but Asymco analyst Horace Dediu has calculated that based on the figures that have been released publicly, that the average lifespan of an Apple device is around 4 years.
Dediu is basing his calculation on figures released by Apple every quarter on how many units they have sold. It is also based on the rare figure of active devices, which Apple recently published to be at 1.3 billion. According to Dediu, by knowing the number of active devices along with the number of devices sold, it can be used to approximate the average device lifespan.
Interestingly enough it seems that the average lifespan of Apple products appears to be increasing with every quarter, suggesting that if anything consumers are keeping their Apple products around even longer than before, and will continue doing so.