Hi M. Junior Evil,
"Heavy Duty" battery cells are lousy and use old carbon-zinc technology. They have a very low capacity and current driving ability and self-discharge (then leak) in about 1 year even if not used.
Alkaline battery cells are much better, especially at high currents. The ones I bought yesterday (with a discount coupon, of course) have a "best before" date of 2011.
I recently did a survey from Energizer, about their new AA lithium battery cells. They claim that they can take 568 digital camera pictures while "ordinary" alkaline cells take only 70 pics. (Heavy Duty battery cells might take 10 or 20 pics if you're lucky!) A big difference. The survey wanted to know how much I am willing to pay for a pack of 4. Packs of 2 now sell for $10.00CAN, about 5 times the price of alkaline cells. They want your money now, instead of later.
If you frequently replace batteries each month you should be using rechargeable Ni-MH cells. They are still good after about 1000 cycles and have about the same capacity per charge as alkaline cells. You can't leave them lying around, because they self-discharge in about a month or two. Also don't use them in the dark in a flashlight if you are up a ladder. Their charge lasts until the very last second then all will be dark!
Energizer have a lot of technical info on their website. Click on "Technical Info" at the top right of their home page.
www.energizer.com