If your headlight lasts 7 hours on 2 AAs, it's not bright enough. I use a Rapid 3 for a taillight and it does the job. That, coupled with the reflective strips on my vest, panniers, and pants are plenty for cars behind to see me. I have a MagicShine 808 for a headlight and run it on high at night. Anything less and I would not feel comfortable. Headlights are very important so that oncoming traffic can see you. You don't want to be invisible from the front. Remember that most car-bike accidents happen at intersections.
You might want to enlist the help of a friend. Ride around the neighborhood with your lights going and have him drive around in the same general area. Ask him if he could see you. For the best test, don't tell him exactly where you'll be.
Finally, remember that even with lights, hi-viz clothing, and a siren blaring, some people still won't see you. Ride as if you're invisible.