Several sources site that in a house with this amount of square footage, air ducts should be cleaned every 3-5 years. the answer on sites varies, but all fall within 3 to 5 years.
You may consider having your air ducts cleaned simply because it seems logical that air ducts will get dirty over time and should occasionally be cleaned. While the debate about the value of periodic...
If you can visually see a lot of dust build-up inside your duct system, or if you have mold in your duct system, it is probably a good idea to have them cleaned. Dust and mold can lead to polluted...
"Air Ducts need to be cleaned at least once a year. Some people clean them twice a year to be safe, or at the beginning of every season if you're really on top of things."
Not really enough information... However, you will need two or three units to get proper zone control, and from 4 to 8 tons of total A/C depending on your location. If you have not had central A/C...