Q1. Battery life depends on usage. Assuming that a single battery powers all the functions in your camera, the more flash you use, the fewer shots you can take off a single charge. Same thing goes for auto focus and power zoom, those too deplete your charge.

Q2. To my knowledge, all digital media deteriorates to some degree over time. The only current solution is to copy your library every 5-10 years to new media. The images will never lose quality per se, either you will be able to open the image or it will be corrupt and won't open. In some instances corrupt files will open, but with bands or stripes of image in the wrong place or on the wrong channel. Sometimes it is possible to fix the errors in PS, but it takes time, patience and skill.

I think the manufacturer has some rating as to memory stick activations, also there are many steps to taking the stick in and out, which could in theory wear down the contacts.

Digital medium saving images for archival use so far is unproven archival range. The technology is young, it is a magnetic wave saved on your hard drive, which has a measured degradation, unknown currently. Most photographers who have any images worth saving would save three copies of the same image. They should be saved as TIFFs, PSD, Camera RAW format, or Adobe Digital negative format, saving them in Jpegs is not the best choice, since jpegs are prone to file manipulation lost every time the file is saved.

In any case if the images are truly valuable, I would do the following, 1) save the original in optical format, i.e. Kodak Gold CDs/DVDS, 2) two copies on two different hard drives, 3) have large image printed up in archival inks and paper save the image in archival container or frame, 4) consider off site storage which has RAID capability, or 5) invest in RAID drives which is the most expensive options.

I've got a couple of Sony cameras, but they are the higher end versions. If you camera uses the more or less standard sony battery, I've found mine hold the charge more than sufficient for several hundred shots. I'd be surprised if you can fill a 2GB before the battery wears down. If you are using double A's, possibly. Does your display show percent battery left or something like that?

I'd just go out and shoot away, making sure to set the thing to the highest resolution possible, and see how much a 2GB will hold. I find I can fill one pretty quick, but I'm doing 10mp each, using raw, so each image is taking up around 25mb.

The little Canon pocket camera I carry all the time won't take anything bigger than 2GB, so I always carry an extra plus a spare set of the double A batteries. I have run out of space on the card and worn down the battery easily in an afternoon's shooting, even if I don't use the movie mode.

Most of these digital cameras have an auto shut off if you carry it around turned on. somewhere between 1 and 3 minutes and you can usually change that somwhere in the settings. Usually all you have to do is press the take picture button and it will come back on, press it again and it will take the picture. I mostly simply turn it off and on as needed.

Most also have several different focus modes. One of them, usually not the default, will continuously refocus, putting a huge strain on the battery. The default is usually not to focus until you push the shutter button half-way down.

As soon as possible after you get back from your shooting, download the images to your computer. Do not erase them off your card until you've made at least one other copy of them somewhere. Then format the card in the camera.

when you bring up your digital darkroom of choice, be sure to save as after you play with the image. If you accidently save over the same image file, your original will be gone. With jpg the main thing is to never edit the original. Copying it (by drag and drop or copy and paste) will not degrade it. What degrades it is saving from a photo editing program and using some level of compression (most photo editing programs will drop down from 100% to something like 80%, which is generally ok -- but if you then save the already 80% compressed file at 80%, dropped pixels might become visible, two or three times and the image is definitely degraded). When in doubt, always safe as a new image name. I generally save to a subdirectory called 'edit' inside the main directory where I put the shoot, e.g. "20080523 nature pics by driveway".

I don't do that anymore, though, since I'm using Lightroom to both manage my photos and do the minor fixes I want. But I do backup everything to another hard drive at least once a day, and usually cut a DVD of at least the originals as soon as I can.

I have a spare battery, which are fairly inexpensive. If I'm out and about I carry the spare, especially if traveling. In a single day with either of my cameras, I've never needed it. This includes shooting over 300 exposures.