On an engine where there are hundreds and of moving parts this is tried and true, on a hydraulic system where you have very few moving parts by comparison, and no break in lube to expunge from the system, and all the pump parts are completely submerged in hydraulic fluid continuously, this is a waste of time and money imo. It’s not done on ANY of the industrial equipment that I’ve maintained in my 20+ years as a mechanical tech or mechanical engineer.
we don’t even change the fluid after a pump grenades from over ten years of continuous use! Filters regularly, fluid rarely-as far as hydraulic systems are concerned.
Departments be separated from each other, they gotta get their story straight!