I've found that the impact on battery life depends on your distance to a tower. The phones I have used will burn battery like crazy to connect to a fringe or intermittent signal.

The other part is: the last thing I want to do on a hike in wilderness is to hear or answer any damn phone call at all, unless it's someone I know and I think it might be a critical situation. I'm out there to purge that rubbish from my mind. It completely destroys the re-sync, the rhythm, the reset. Otherwise I might as well hike in a shopping mall. My 2c.