Something I did on my Original was install exterior fans..
Well when it finally failed (Died of old age) my Service technician pointed to the "Crud" that had collected on the bottom of the outside heat exchanger.. It was not (yet) serious but it was perhaps 10-20 percent blocked.
NOTE: In 14 years I never did any work on it save defrost. It worked for the most part flawlessley (Oh one time it failed but it was a dirty connection. Unplugged and replugged the comm wire between the control box and the eyebrow a few times and all was good again.
Very happy with it... But as I said constant operation for at least 11 of thosew 14 years.
Alas it's now out of service for reasons that have NOTHING to do with it. (Entire RV is out of service)