Is my battery life as bad as I imagine?

I got my macbook on Friday... and it seems like the battery runs down really quickly if I stream video. Earlier it said 1:49 at 79%. Other times the remaining charge time was longer than that, but that shocked me. I had hulu open (thats where I was streaming videos from), and probably about 4 other webpages open - 3 as tabs in firefox and 1 in Safari. I also had a FInder window, iChat, MSN messenger, and possibly skype messenger running, but was only chatting with 3-4 people on iChat. The brightness was 3 bars from the brightest... so really not full lighting.
Last night as a test I quit out everything but Pages, Preview, and a Finder window, and the battery life claimed it was like 4+ hours.
Is it possible that the 1:49 at 79% was just a misreading?

If you're getting that number consistently, then it could be a problem. If it's just once, then it's very likely to just be a fluke as misreadings happen on occasion.

the streaming might have taken up some of your cpu and most of all it spins up your hard drive, which will have an effect on your battery life

the time counter does change depending on what you do, it's not strictly given that everytime you hot 80% you will have 3 hours left, keep that in mind

I spoke to apple today and the guy said that the counter tries to be predictive, and also that after about a month the battery "breaks in" - he said, for instance, his cell phone battery is way better now than it was a month ago. So, I'm gonna stop obsessing because the computer's great LOL and I have to stop trying to find problems with the battery life!