>>skille+(OP)
I think the challenge is: Does your hardware support the updates? Hardware vendors from time to time have the tendency to change the OS in ways that it works nice on brand new hardware but is very sluggish on older hardware - to the point of being unusable.
So if I get an update 6 years in that renders my phone unusable, I haven't gained anything.
I would prefer 7 years of sec updates in that case.