Hi Scott,
A good question and the answer is yes, you can and many do it. Easily done in PI with ImageIntegration tool :-)
You can/should also combine narrowband channels to create a synthetic Luminance that will show more info as opposed to using say Ha alone as a Lum.
Here is a link to a bit more detailed discussion:
http://pixinsight.com/forum/index.php?topic=6042.15