We built our house almost 12 years ago, and I've heard that generally the life-span of an HVAC system is around 10-15 years. Every spring and fall you hear ads for system tune ups, and I always wonder if I should do this.

You want to tune it up? Take a garden hose and hose out the exterior coil. If the furnace filter has been kept up there should be no need to clean the interior coil.

So long as it is cooling properly, you shouldn't need to do anything else. I have a few dozen units that are 25 or older. Now I grant you that I am changing several of those a year right now, but they have lasted that long. The oldest one I have running is a 1966 vintage, I believe. The only routine maintenance we perform is to hose out the outside coil in the spring.

In the fall, I called the company who installed the system and actually got a technician and not a sales person. :) He told me that if the system wasn't giving me any problems, that a tune up wasn't that big of a deal. He said it was more of a peace-of-mind issue.

That's right.

With the age of my systems, should I have someone look at them regularly? What are signs of trouble I should be watching for?

Why look for trouble when you aren't having any? If the thing is cooling without trouble, then leave it alone. If it malfunctions, it won't cool. The most common malfunction is a freon leak; the first symptom of that will be either (1) it ices up or (2) it just doesn't cool but the compressor is running.

About the Author: Jim Locker is a technical guy who has done a lot of real estate investing and landlording. The experiences he writes about and advice he gives are either first hand, or in answer to specific questions posed by others. He is commonly known as jiml8 around the internet.