My 330 seems to be rough on batteries as well. I originally had a 246, but upgraded to the 330 after the 246's LCD went out within 2 weeks of purchase. The 246 seemed to sip on its juice, even though it used 2 AAs.
I think part of the problem is that the 330 uses 3 AAs, and my charger only charges in groups of two. (I don't use the scanner to charge the batteries because of the heat.) I bought (12) 2500s, labeled them and rotated them out (4 sets of 3). After they were all used up, I would recharge them in 3 groups of 4. The battery performance seemed to steadily degrade until they would only work ~1/2 hour on a full charge. I assume that the differences in the remaining charge affected the recharged voltage. Not sure though.
I usually just use the AC adapter at home and a car adapter for the road.