With Fraps, it seems you have to set it to capture at 60fps, otherwise the game lags.
For me, full resolution and 60 fps means around 4GBs for 2minutes 22.
Be sure you have a fast defragged hard drive. Having a Raid 0 to capture to does help me a bunch.
Of course after you capture, you encode to something else. A little AviSynth knowledge can help for combining video segments.