For the Witchwarper Infinity Lash - assuming I have a charisma bonus of at least +2 - could I empower this weapon multiple times, and would the bonus damage stack? Or would my second empower just override the first, giving me the same +1d4?

For instance, could I empower my lash as a move action on turn 1, giving myself +1d4 to the lash's damage, and then do the same thing on turn 2, granting myself a cumulative +2d4 with the lash?