We did a complete renovation on an 80 yr old commercial building about 25 yrs ago. Upper 2 floors were office spaces while the main floor was retail space. I put about 80 floor mounted cabinet type fan coil units in the office spaces with hot water heat and chilled water cooling.
The units had a nice off white baked enamel finish. But, the GC's superintendent who knocked back about a quart of liquor every day (on the job) told the painters to paint the units with the same white latex flat they were putting on the walls.
We did a lot of hot and chilled water systems over the years, and installed hundreds of these type units in both new construction and renovation work. Its not unusual to see these units at 25 years old and the factory finish still looking as new. But that flat latex was the nastiest, most hideous looking mess you could imagine within 6 months. I'd imagine by now they've likely been repainted a dozen times, with every repaint looking worse than before.