I use an iPad 2. Remember those? They came out just after the blackboard and chalk I think. A solid slab of non-retina tech of 2011 vintage. And an iPhone 4S, from the same year.
And they still work pretty well. Mostly. 4 years is a long time for mobile devices, but amazingly they're both compatible with the latest software release, iOS 9. I've installed it on both and my impression is that it's quicker and smoother than iOS 8 on both machines. So my old kit can soldier on a little longer. Genuinely good customer service from Apple.