elephant_

I worked in a couple of the stores (Roseville, Sacramento Macy's, and Carmel), and we'd have people often asking if the expiry is really when it says it is. I'd push it and use 'em a couple days after the fact, but they really are more effective if you use them fresh.

Think of them like dairy - if they've been left on the counter for a while, toss 'em. If they're just a few days past expiration and been kept cold, you should be alright.