Air duct cleaning

I have been reading a lot of articles on heating and cooling lately. Many are suggesting that everyone should have the air ducts in their home cleaned regularly. I feel that, since knowledge about this topic is in its early stages, significant amounts of research is necessary. The other day, I came across an article that said studies have not been shown that duct cleaning can prevent health problems, and are just possibly one of the reasons. It said that the only time you must absolutely have your ducts cleaned is if there is substantial mold growth on the heating and cooling system if the ducts are infested with vermin (this one I feel is a give-away) and if your ducts are so clogged with dust and particles, you can actually see it coming out of the register. Some articles say that cleaning your heating and cooling system components may help better operating, so to do both at the same time. I feel as though it might cost me a lot of money to do all of it, but I think it is highly important to make sure you are breathing quality air, regardless of what certain articles may suggest. I feel as though I will do a bit more research about all of this before I dive into anything. I know that in the long run, heating and cooling maintenance will help save on energy costs and that will eventually be very helpful financially. I just think it is important to stay up to date on the newest innovations and studies to make sure you are living a healthy lifestyle.