[TonyC]

To tophcfa:
If your Apple 6+ phone is working fine, then there is nothing to stop you keeping your phone as long as you like. You just will not be able to upgrade to the latest iOS release.

Apple is always improving both the hardware and software in increasingly complex ways, so you will not be able to take advantage of the new functionality. But the phone should continue to work. Apple makes sure all new phones will be able to get iOS software upgrades for five or six years. After that you cannot upgrade, and you can either keep your phone at the latest release that you upgraded to, or get the latest phone, which will be much faster, better and with more capability than your old one.