What's the greatest extent (as in the most amount of time) to which you've eaten something past its expiration date with the food still being enjoyable?
I'd hazard a guess that they're just taking pity on you for not having an older fridge. Many appliances made 25+ years ago are still working just fine, perhaps with a bit of maintenance, but nothing made in this century is built to last.
My mom's fridge is over 30 years old, as are her washer and dryer, and all three are just chugging along like champs. My refrigerator is just about 25 years old and the only thing wrong with it is the gasket on the lower door needs to be replaced soon.