[Insoc]

It is a computer with a phone in it.

Get a very small phone, that you can buy minutes on. Carry it for emergencies, if things are that important to you. Redundancy is a key to stopping a critical failure. Also, you might be somewhere where your phone won't work, and that has nothing to do with a battery, so your desire as honorable as it sounds, has holes in it.

COMPROMISE. Sometimes, you cannot have it all.

Always remember a new phone's batteries take some time to break in. There is a solution to every single complaint you have. You just need to choose one.