if you really want the 4.2.1 then you can update to a custom withed00r firmware (is a custom 3.1.3 that has all visual stuff from 4.2.1). Should be easy to find the withed00r firmware with google, and it said the batery life is very good on ths firmware.Let me know if you was able to do it, if not if you want I can do it online for you, just PM me