I also noticed that my Google Wallet cards no longer have expiration dates- when a card expires and they issue a new one, the Wallet card works without any intervention on my part
That's very much contrary to my experience just a couple months ago that I detailed in another post: https://news.ycombinator.com/item?id=47981956
Wallets usually don't store the card information directly anyway, but only a token, which can be re-associated with new underlying card details when the card is replaced.
The token itself does also have an expiry date (it's a mandatory field in most protocols), but that can be updated as well, I believe.