Update - Following some trial and error, it turns out that nothing was wrong with my setup and there was no interference with other wireless devices in use. The culprit was the brand of battery used. The Duracell Ultra AA batteries were of very poor quality I am guessing and probably from as bad batch. Using Sony AA batteries since the past two weeks and the mouse battery level is still at 100%. With Duracell, I would have had to change the batteries twice by now.