I go hunting to get away from all that. I do carry my cell phone, completely turned off, just in case I need to call for help, but it stays in my pack otherwise.
To begin with, I don't let my cellphone intrude on my life. So, I never feel the need to "get away" from it.
Even if I did... In the mountains, I may not have the time to wait 2 to 4 minutes for a smart phone to start up, should I need to make an emergency call. So, I keep it in Airplane Mode. It only takes about 5 seconds to turn off Airplane Mode and start searching for a signal.
This year: With about 1 hour of transmitting/receiving (acquiring a signal, checking 3 voicemails, sending/receiving about 12 text messages, checking for a weather update, and sending 1 photo), and 30-45 minutes playing some games on that rock face.... The battery charge lasted more than 5 days, and the phone was only turned off completely at night (1-2 am to 7-8 am), to prevent the cold temperature from affecting the battery's discharge rate.