I’m tempted to say when you can’t read the old prescription, but in all seriousness…

I think that’s a question for your doctor. Different brands and types of lens, not to mention the current condition of your eyesight as opposed to the last time you had it examined, would be the determining factors.

What do you mean when you say “expired?” Do you mean the prescription needs to be updated because you can’t see that well? Do you mean the lenses are in a box, unopened, and they may be a year or two old? OR do you mean you’ve been wearing the lenses and they are getting cloudy or dry, or chipped?

Mine have a date stamped on the box and on each lens container. Where they are past the date, they are still comfortable and they are daily wears so I have a whole mess of them.

Welcome aboard by the way.