iPhone 4 Power, Wake / Sleep Button Not Working

My iPhone Power, Wake / Sleep Button has recently become unresponsive. Having to push really hard to make it work. Today it seems completely dead.

I took it to the Apple Store for them to look at. As it is out of warranty it will cost £119 to replace. I need to think about this before i replace it.

The genius told me about AssistiveTouch and how i could use that to lock the screen.

My only concern is if the iPhone crashes / freezes, the battery runs out, i won't be able to restart it by holding down the power / home button.

Is there away to restart the iPhone if it freezes without pressing the power button?

The genius mentioned that if the battery died and i connected it to power via the usb cable and it would work.

If it froze would connecting it to the power restart it?

Thanks.