Only with the upcoming iOS 8 release have Apple ended support for the iPhone 4 (the 4S remains supported), a phone released over four years ago.
I'd say that's pretty good going.
I'd say that's pretty good going.
Nevertheless, no one is forcing Apple to pour their profits into extended support for older models.
If anything, the incentive is to end support sooner and push consumers to trade in their old devices for newer models.
Very few people keep the same phone for ten years; most people upgrade every few years, such that their high-end phone never becomes deemed a low-end unit.
If you're particularly cost-conscious, and don't see the added value of a high-end phone, then buy a low-end phone.