Just bought a new Nikon D5000?

And I would say the battery lasts for about three to four hours if I'm taking pictures non-stop! When I got it like 3 days ago, I charged the battery for about two hours. The intructions say that that is the time needed to fully recharge it. But shouldn't it last longer? Did I do anything wrong? Should I have charged it the first time longer? Please give me your feedback! And also how much pictures should I 4GB card hold? I thought about 900, but it only holds like about 300?!
Please answer all the listed question!

Yeah i have so many cameras and the batteries don't last
i've tried built in batteries
rechargable aa batteries
regular aa batteries
and nothing holds
it should hold way more then 900 if i'm correct
i have a 1GB and it holds 200 and my 1.5 holds 600

First, the battery charger should indicate when it is full. Usually on new things, you charge the battery for about 5 hours. It should say on the first time setup guide.

if you are taking pictures non-stop, well, of course your battery will drain. Battery life mostly depends on how many shots you take. The most shots I have gotten with my D40 is about 800, but I look at my screen constantly.

as for your memory card, my 4gb card holds over 1000 pictures on the highest jpeg setting. Once you go to RAW format, that will almost cut in half.

That's about the correct battery life. You can increase that by buying a high mAh battery. The one you have is probably 12. If you buy a 15 it may go another hour. But again, this is the expected battery life.

The amount of photos a 4GB card will hold depends on your camera's settings. If you're running at the highest setting the camera is capable of, which I recommend, the count will be less than with a lower setting. Did you format the card in the camera? Not in the computer but in the camera? If you can upload do so and format the card in the camera before shooting again.

Also just do the math. Look at one of your uploaded files. Check the properties of the file for its size. Divide that into 4gp - that number will be about what the card will hold.

A nikon DSLR charger will tell you when the battery is full. The first two or three chargers you will not get full capacity. After that 600 photographs should not be a problem but if you use the screen a lot, shoot video or flash often this will go down.

With my D300, which uses the same sensor, I get about 500 shots in RAW on an 8gb card