leaving ink on windmill system

Good question… I leave black rubber base on my windmill for a week at a time; it doesn’t help or hurt. I use an overnight spray to keep the ink from drying on the press.
The only thing that has hurt my steel rollers has been the water-based ink, and It doesn’t have to be on the press very long to leave a pattern in the chrome. But one job could pay for two windmills. It doesn’t affect inking at all.

The only time I’ve EVER heard of leaving ink to dry on the ink train as an intentional method was in a Q/A column from the ’30s, when composition rollers were the norm on job presses, and all ink was oil-base. It was also best practice then to have different sets of rollers for light and dark colors. But if you only had one set, and had a problem with previous dark ink persisting into lighter runs, the answer was let the light ink dry on the rollers as a barrier to the pollution beneath. YMMV!
I have worked in situations where non-oil-base ink was left on press, maybe sprayed with a little overnight spray for preservation or next-day run-up. But that was to save the time needed to wash up at night and try to ink to the same color for the next run. That can be a real efficiency in daily book work, but all the inks I treated that way are long discontinued except for rubber-base, which is the least-drying ink ever invented.

Agreed parallel. Overnight spray impedes drying on the sheet also. I always make sure the job allows the ink to dry by absorption, and test some sheets first.

Never heard of leaving ink on a press overnight, but that was before rubber based ink, however on long run bookwoork we did leave the ink in the duct so as to keep the duct setting, so we had a way of cleaning the duct roller of ink and covering the roller with machine oil. The ink in the duct was then covered with a wide strip of paper that had been soaked in oil and that would stop the ink skinning over ready to use the following day.