Where mechanical watches just stop when run for a long time without service, Accutrons are strong enough to keep grinding away. Here's the ruined index wheel and pinion from a 2181 that was recently on my bench. The watch was still keeping time pretty well, but starting to lose a bit, leading the owner to send it in. The upper pivot has a shoulder worn into it, and the lower was spinning in a pile of rusty grit that filled the space between the jewels and wore the pivot into a point. Sometimes I find pivots stuck in the jewels, twisted clean off, probably when someone puts a battery in after the watch is sitting for a long time.