The dual switch controlling the bathroom lights began requiring some fiddling, which was not to be tolerated. After replacing the switch, I cracked the old one open to see what’s inside…
The failed side of the switch controlled the lights over the sink:
The side for the ceiling vent fan + light got much less use, still worked, and look a bit less blasted.
Not much to choose between the two. It’s been running for nigh onto two decades, so …
The Smell of Molten Projects in the Morning 
My house was built in 1986 and several switches have similar failings. I went to Lowes and purchased a contractor’s pack of switches. Apparently they have a 30 year life and since they have similar usage they are failing nearly simultaneously.
Aye!
The fluorescent tubes in the Basement Laboratory used to get flickery in groups, because I installed all the fixtures at once. Now they fail more randomly, but it took a decade to get there …