Ideally every 6 months by a professional

A 10-year major parts warranty is offered by the manufacturer

One that is sized properly for your home and fit your needs as suggested by an HVAC professional.

There's a few ways to know when it is time for a new system. Examples are it'll stop working, your electric bill would rise, or you'll wake up with a bad taste in your mouth usually caused by mold.

The air filter should be checked every 30 days

You shouldn't clean an air filter only replace and change them every 1-3 months.

The air filter should be changed every 2-3 month and more often if you have pets or smoke in your home.

There is no proper humidity level, it all depends on your comfort level.

Yes, it's always a good idea to have your ducts cleaned, especially if you want to improve air quality and air flow.

It all depends on the size of your home.

The best way to heat and cool your home is by having a licensed professional install an air conditioning and heating system.

It's not a simple answer because each one has benefits and qualities that would fit each individual's homes and needs differently

If the air quality is bad you will start to see dust building up quickly, get sick frequently or wake up with a bad taste in your mouth. In which case it is time to call a professional.

You as the customer are unable to properly check the air quality. You will need a licensed professional with proper tools to be able to check the air quality.