Per William Sommerwerck:
You've said this before. My Sonicares have lasted from two to four years.
And that's buying them in pairs at Costco.

You must be recharging them in a way I am not. How often do you drop them
back on the charger?

In the instructions for my Oral-B's, there is an admonition to
totally drain the battery and then recharge: every six months for
the "1000"s that I just bought and monthly for the "Vitality"
that recently died.
--
PeteCresswell