my glasses prescription doesn't have an expiration date on it. Zenni and Coastal don't care if I order new glasses using my old prescription. I haven't tried with contacts... I think my last prescription had an expiration date.
Note on contacts: because you're physically inserting a medical device into your eye, part of your annual exam is making sure that you are not causing any (potentially permanent) damage do your eye. While hopefully you are not abusing your contacts, even in normal use, sometimes the eyes can be harmed, which can cause major problems down the road for you. In my opinion, the expiration is probably a good thing if you're proponent of trying to protect people's eye health.
Yeah, I'm fine with it for contacts. It's just protectionism on glasses unless the prescribee has some degenerative condition.