I've used the Cyclemeter app for years to track rides (since iPhone 3gs days) and have generally found my phone battery survives almost all of the time.

Earlier this year I did an 87 mile ride (~10 hours total time; more stops than I needed for sure) and my iPhone 5 battery was exhausted around mile 55. I even turned off most extraneous functions to give me max battery other than BT so I could use my Wahoo HRM.

This past weekend, I rode 65 miles in ~10 hours while sweeping the last 35 or so miles of a ride route and was pleasantly surprised to see that I had 40% charge remaining at the end on my iPhone 5s.

It appears as though the M7 motion coproccessor isn't all marketing fluff. I've read that it uses 1% of the power required for GPS functions when they run on the main processor.

Now all they need to do is split BT off from the baseband (bundled with WiFi I'd imagine) and the HRM, cadence and other stuff would also be less power hungry...