Should they do the routine checkup before they turn it on? Is now the option? to say, hey, let us come in, just do the quick inspection and get it cleaned up and get ready for winter?

Ideally, the best time is just before it gets really cold.

Furnaces get tested when it's usually below 10 degrees.

So that's when they start running more constantly.

Most furnaces are set to run the house at zero degrees.

Below zero degrees is when they will start to struggle.

And that's when they'll get tested.

Does that drastically affect efficiency? What's the best part of the duct cleaning? Is it really important?