On 20/05/2020 21:46, NY wrote:
.... snipped

We've not had the laser long enough to use up the cartridges it came
with, but I'm preparing for "ouch" prices when we need new ones. But
they last indefinitely until the toner is used up - toner doesn't "dry
up" if you don't print a test page every so often.

....snipped

Sadly it seems that toner "does" degrade. I have an infrequently-used
CLP680 colour laser printer and a couple of years ago complained to
Samsung that the print colour had become poor. Their answer was that
toner does not have an indefinite life. I changed the toners and the
problem was solved.
FWIW I've always bought my toners from stinkyink