I've had an iphone 6S since new, which I think was in the spring of 2015. It's still working perfectly. There was a deal where they kind of acknowledged they botched the battery life, so I got a replacement for $37 including sales tax. I use mine heavily, and it's going strong. I use a Quad Lock mount to mount it to my bike handlebars. I run the ridewithgps app. I mount an external battery to the bike frame to keep the battery charged while I ride. This way, I don't need a separate bike computer. I got Quad Lock mounts for my wife's cars, and I got her a Quad Lock case for her iphone, so the phones twist in quickly and easily.

Here is the battery mounted to the bike with a velcro strap, a heavy rubber band, and a ball bungee.