[firecontrol]

Pros and Cons on both sides of this one.

If you set the fan to run all the time you get two things:
Pro? First of all you will more than likely accomplish averaging the temperatures throughout the house. IE: If you get temperature differences between different areas of the home during the off period and they are big enough to make you uncomfortable, then running the fan in the "on" position will help to eliminate this somewhat.
Con? The second thing that running the fan all of the time with the equipment being in the attic is the possibility that the air the unit will distribute to the home will be warmed up by temperatures in the attic and will actuall make the unit run more to cool this extra heat load down and thus will cost you more in your energy bills.