Will the battery’s life be shortened if you leave it on the charger overnight?
Yes.
Will it be shortened by a meaningful amount?
No.
As in … wake up in the middle of the night the moment it’s done charging to take it off the charger, and it might be seven years before the battery falls below 80%. Leave it on the charger all night and it might be six years and eight months before it falls below 80%.
But, one thing is for certain: if you interrupt your sleep every night just to baby the watch’s battery, your own lifespan will be diminished, along with your quality of life — and in significant ways.
Use the watch as it’s designed to be used. Accept that it will eventually fail and that, not only is there nothing you can do to prevent it from failing, there’s nothing significant you can do to delay its failure. (There’s plenty you could do to hasten its failure, of course, such as smashing it with a hammer.)
And … “pro tip:” this is true of everything, even the Earth, even the Sun, even the Universe itself.
Even you yourself.
b&