I know air conditioning. It's my life. If someone were to tell me what kind of system they have, what color it is, and what its symptoms are, I could probably tell them what's wrong with the system over the phone. It's not just age and experience, but the art of listening; listening to the customers, listening to them talk, listening to their explanations of the problem.
Have you ever been on a service call and used your troubleshooting skills to figure out what was wrong only to find out that the customer already knew what was wrong? If you asked them some questions and listened to them, you could have fixed the problem and been on your way.