DTPO on MacBook Retina: Why use the 650M?

Hello, I notice my Retina MacBook Pro switches to the discrete chip when running. Is there any reason for this? When using the 650M chip, I get several hours less on the battery with the discrete chip in use…I can’t come up with any reason the integrated Intel chip can’t be used…

Thanks,
Dan

Generally this switch is caused by using the CoverFlow mode.