I represented several high-end appliance lines for several years. Among them were Viking and Sub Zero. My personal choice is Sub Zero because it is not only a fantastic refrigerator, but if you ever have problems, the factory will go to the end of the Earth to make sure you are satisfied.
Some things that happened in my territory:
Complaint: A guy complained about moisture around the door on his discontinued model that was fourteen years old. It was out of warranty, of course.
Solution: Sub Zero replaced the refrigerator with the current model, and covered all associated costs, which included installation labor and freight.
Complaint: An old lady had problems opening the door on her ancient model.
Solution: The factory sent weaker door magnets, and paid her local dealer to install them. There was no charge to the lady, even on a 25-30 year-old unit. It was so old that no one I worked with was familiar with the model.
Complaint: Not one, but two model 501 freezer units died at a customer's house. All the contents were ruined, of course.
Solution: Another brand freezer was purchased by Sub Zero, and it was immediately delivered to the customer's house as a stop gap fix. Then, a Sub Zero engineer personally walked down the line while a replacement was being made. Then, he and the rest of his team personally tested the unit. Next, the freezer was loaded onto a pickup truck, and the same engineer drove it from Madison, Wisconsin to Nashville, Tennessee. Then, he supervised its installation. After that, he gave the customer a check for all the food that was lost along with the company's most sincere apologies. The stop gap freezer of a different brand was also given to the customer. Now, he had a freezer in his garage for free. (The original problems were sabotage that happened to a few units during a labor dispute, by the way.)
At a National Kitchen and Bath Show I overheard two GE engineers talking while they were inspecting a Sub Zero Model 550. "This is what we could do, if we worked for a company that specialized in refrigeration." one said. The other guy agreed.
To me, it is a no-brainer.
Refrigeration will last 50 - 200% longer if the coils, condensers, etc. are cleaned of all dust [and grease if you fry a lot] at least twice a year.
The energy efficiency goes down the tubes when the components are dirty.
The manufacturers & distributors will not inform you of that for obvious reasons [who reads the manual?].
zz.
Sub Zero does, and many maid services have it on their "to do" lists.