Sprint seems to confirm that killing apps may be a good idea to prolong life. Makes sense to me, I know this is an area of debate (to ATK or not)...
"In general, the less frequently you allow these applications to update, the better your battery life. If you find there are applications you don't use at all, for the best battery life experience, configure the application to either not sync at all or to sync at the lowest frequency. You can also end the application or service by going to the
Running Services Widget mentioned above."
http://support.sprint.com/support/ar...0100601-130442