Re: air ducts / dryer vent cleaning
What RBA suggests has worked for me with cleaning the dryer vents.
As far as duct cleaning goes, my buddy is an HVAC guy and he recommended getting ductwork cleaned every 7-8 years. Says it will pay the cost of doing it back in efficiency for your heating/cooling system. We did it when we first moved in to our house, so I don't know if it really helped or not.
When all is said and done more is said than done.