If you want stability and battery life, why not buy an iphone? I hate iphone to the depths of hell but there's no doubting they get apps before android, are generally more stable then android apps and the battery life is generally much higher on iphone. Basically by buying an android and not rooting it your saying "I don't want functionality, speed, customization, stability and increased battery life"
And while yes, there is a risk of flashing custom ROMs, phones like HTC One X and SGS3 have so much support behind them, all problems when rooting/unlocking bootloader are fixed with tools to un-brick your device easily if things do go wrong. The failure rate on doing this now-a-days is very very low, almost as low as your SGS3 exploding *wink*