I suspect that would depend heavily upon the brand. I only have experience with four notebook computers here:

IBM A21p -- battery still fine after several years usage, mostly on mains.

Dell Inspiron 3500 -- battery still fine after many many years, almost entirely on mains.

Dell Latitude C850 -- battery still fine after a few years usage, mostly on mains.

Toshiba 5000 -- battery croaked early on, got replaced, unit got sold.

Cheers