Thanks for all the imput.
Actually I wasn't asking for medical opinions. LOL.
The main point of the question was-- should the ducts be cleaned or is it something that is unneccesary because the filter works fine.
The house is about 15 years old, but I have noticed some dust around the vents. However, I changed the filter and it is an industrial strength $40 one-- the size of an accordian. I guess it is always useful to tune up the furnace and AC. At this point, it sounds like I should pass on the vents for a while.