While not often discussed, Avid Andy has been known to have some serious flashbacks. Hallucinogenic drugs from parties long ago or dropped one time too many times as a child, your guess is as good as mine. Andy recalled the time, years ago when we just stopped performing maintenance on exhaust fans under "x" CFM. Sure, reliability advances in the product, declining costs, were all contributors to us changing our maintenance routines. Could it be time to once again re-assess our approaches, this time on unitary systems under "x" tonnage? Do we have any idea how to even approach such a decision? Certainly IIoT promises to give us more information in the future, once we have the data to model; however, might we reflect back on fundamental logic around MTFB (mean time between faults) and EOL (end of life) calculations. My favorite visual is sketched as the image above, some liberties to the traditional "bath tub" theory were taken. ...