Generally, how long do AA batteries last in a digital camera?

I'm shopping around for a digital camera to photograph slides (under a microscope). I've never owned a digital camera before and I just need to know if you can count the battery life in number of photographs or in time used and how long the lifespan is.

For quality of battery, I'm going to say Energizer (regular) or Duracell (regular). AA batteries only. I'll be using it about 2-3 times a week for no more than 2 hours each time. I don't know the flash. I just need an estimate so I can know how often I'm going to need to replace the batteries and if it will be worth my time without regard to the rechargeable batteries. I guess what I should ask is, can I photograph about 100 slides with one pair of batteries. Will I need to constantly carry batteries with me to take that many photographs?

if you go on manufacture sites
they will tell you how many pics
the different types of batteries will get

hhow much do you use you cam?

This greatly depends on the quality of the battery, along with the camera, and other factors such as flash. Personally I have not tested the battery lives, except that in one of my digital cameras I have re-chargeable batteries, and have done about 70 photos in one day and not run out the batteries, then every night I charge the battery. I'm sure that depending on several factors you could take more than 100 photos without flash on the camera.