“In The Number, I provided a model for estimating the number of active Apple devices at any point in time. The relationship between active devices and cumulative devices sold gives us a rule of thumb that says that 2 out of 3 devices ever sold are active,” Horace Dediu writes for Asymco. “I propose now that knowing active devices and cumulative devices sold allows one to determine the average device lifespan.”

“The cumulative retired devices can be calculated as 2.05 billion cumulative sold minus 1.3 billion active or 750 million. The time when cumulative devices sold reached 750 million was the third quarter 2013. The lifespan is thus estimated at the time between now and Q3 2013 or 17 quarters or about 4 years and three months,” Dediu writes. “Note that cumulative devices sold includes Macs, iPhones, iPads, Apple Watches and iPod touch.”

Dediu writes, “I’ll show in the next post how this single number allows us to calculate the net present value of Apple’s future cash flows, or, by definition, Apple’s enterprise value.”

Read more in the full article here.

MacDailyNews Take: As we peruse our collection of Apple devices in use today, from iPad Air 2 units to iMacs, to iPad Pros to Apple Watch Series 3, to iPhone Xs, MacBooks, and more, the average lifespan of 4 years and three months strikes us as a dead on estimate*.

*As long as we don’t power on our Macintosh 128K. 😉