You know, I've often wondered what owners of really extensive car collections, that all sit in climate controlled garages, do. My car sits in a climate controlled garage, and I now put a few hundred miles on it a year -- less than a thousand. Every year I send a sample off to the lab and they check for the usual wear elements,
zinc & phos, and the like, plus they look for moisture,
antifreeze, fuel and a TBN as well which you can compare to the TBN of your pure
oil. But I don't just change it to change it -- there's just no reason to.