Battery Calibration

How dead does it have to be?

I have already run the battery down to zero left it over night and started it up and it had 2% so I ran that down again. Is it now suffice to say that it is dead? Or should I leave it for the rest of the day and try to turn it on and run it down once more - if that is even possible?

I have the latest Macbook Pro 15" high res.

P.S. I only got about 3.5 hours out of my battery nothing intensive watched an hour of video form the hard drive and surfed the net, is that expected or am I getting bad performance?