Just under four years for the first.Once in two years, three years?
No idea as I haven't performed a statistically meaningful survey. Why does it matter? People vary. Some replace more often than others.Would I be right in assuming that people upgrade their smartphones much faster than they do tablets?
I am using an iPad 3. Since, I did not upgrade the OS beyond its native iOS 5; haven't felt the subtle pressure from Apple to upgrade hardware; with their one-way tickets to OS sluggishness.