I too have used sour cream up to 2 months after the date on the carton, with no problems.
I have also cut off the mold on hard cheese, and used the rest of the cheese.
Twice, I have had bar cheese from the grocery store get the blue moldy spots BEFORE the expiration date. It was the store's dairy brand. Both times, I took the cheese back to the store with my receipt and got a refund.