Greg/Groschopp: there are a selection of failure modes. Heat can result in lubrication breakdown, wherever the grease or oil solidifies and ruins the gears.
Greg/Brevini: cleanse oil can maximize gear life drastically, https://adamppzr193883.pointblog.net/not-known-factual-statements-about-gear-gears-gear-technology-gear-design-gear-automation-71120745