Away from home - fast screen off and lock

Your phone is at far more risk of being stolen when you leave home. so turn the screen lock on with a faster screen timeout.

Battery critical : gracefully degrade

Never pick up a flat phone or tablet. Saves as much battery as possible when it's getting low. Use of airplane mode allows you to quickly turn everything back on if you need to.

At home - slow screen off and lock

Your phone won't be stolen when you're at home. So there's no need for the screen lock!