For instance, my MacBooks tend to be in use 5 - 10 years because they get handed down, and I essentially only run MacBooks while they're plugged in (e.g., off power less than one day a week), and have never had that happen.
I certainly see battery capacities drop after 3 years or more, and simply buy a new battery.
I'm glad you haven't had this issue before, but I'm willing to bet that the (admittedly not often) time you spend unplugged has prevented it.
I've run several laptops as you describe without issue, however I've also run two macbooks at two different times plugged in 24/7 as "servers" and both had this issue within 3 years. The first of these two shattered the glass trackpad which was a safety issue in itself. Apple agreed and fixed it for free even though the warranty had expired!
This happened to one of my Dell laptops last week since it had been docked for a year and already had a worn battery. So that's why it was fresh on my mind when I commented. Luckily I caught it because the plastic case bent upwards...
For instance, my MacBooks tend to be in use 5 - 10 years because they get handed down, and I essentially only run MacBooks while they're plugged in (e.g., off power less than one day a week), and have never had that happen.
I certainly see battery capacities drop after 3 years or more, and simply buy a new battery.
OWC "MacSales" batteries: https://eshop.macsales.com/shop/Apple/Laptop/Batteries