Android - How do I keep my Android 4.0.3 phone awake when USB connected?

I have checked on my two Ice Cream Sandwich Devices (Stock Xoom and Droid 3 running CM9 Beta). I have, under Settings > Developer Options a Stay Awake option. Which keeps your device awake when charging.

This will work if your device charges over USB (my Xoom does not, for instance).

However, should this option not be there, we can turn to apps for help!

StayAwake looks like it could be a solution to your problem.

WakeLocker for Galaxy S also looks to be a solution.

The Samsung Galaxy S II does not have this feature, and never has, because of its AMOLED screen.

They burn (like CRTs) if they have the same picture on the screen for too long. For some reason apps can still lock the screen on, but you can't do it from settings.

(My Samsung Galaxy S II has burn in from the notification bar.)

You can use StayAwake, just don't forget to turn it off.

On my Galaxy Nexus it can found under

Settings/Developer Options/Stay Awake.

YMMV.