I have a 13 year old Ruud Silhouette system (dual zone). Ruud model number: UGDJ-07AEUR. I had been running a do-it-yourself-installed humidifier in each unit. They sprayed mist into the airflow. They were replaced last year at which time scale was seen on the coils and condensation pan. This year the scale is flaking and causing water to overflow the pan. I had two experts out who offered either to replace the coils or replace the system. The argument for the bigger job was that the older refrigerant will be phased out and if my compressors fails soon, I would need new coils again to match the new refrigerants.
There was also a worry about pitting of the heat exchanger, though this cannot be viewed unless the coils are removed.

Due to the age of the system, I have been advised to consider newer high efficiency systems.

My questions:
1. what is the life expectancy of my current compressors?
2. Are these compressors really likely to fail soon, making the coils only solution a potential waste of money?
3. is damage to the heat exchanger really likely?
4. is there a way to diagnose that problem easily?
5. what do you recommend? Go for a whole new high efficiency system?

I would get another opinion,, don`t tell them anything,let them tell you

1.if taken care of,, guess is all anyone can do (15-20 years)
2. know-one knows could last 10 more years
3. my thoughts not likely,, but again (just a guess)
4. get the coils cleaned up and hope for the best
5. I would see how many more years it could last

I agree get a second or third opinion, but don't say a word to them.
Also r22 is not being phased out completely. Yes theys top making it next year. But it will be around for 60 plus years. I can still get refridgerant they stopped making 60 years ago.