Get an extended battery.
I mean, who wants to turn off features, leave your phone alone, or turn off your phone all together. TOTALLY defeats the purpose.
Imagine i bought a Ferrari, but the gas kept running out, so i just decreased its performance, left it parked in the garage and eventually just threw away the key. Sounds silly doesnt it?
These smart phones are mini computers, we love to use them all day long. The only real answer is either stay by a charger, or get an extended battery, the largest you feel comfortable with, or buy 2 and swap them out. I love my laptop, it plays any game i throw at it, but it eats through 9cell batteries like no other. So i have 2 batts and usually stay by a charger. Same with my phone, i have the extended batt and 2 stock batts as backup.