Do receiving addresses expire on Multibit?
But to answer the question: addresses do NOT expire. Not in Multibit, not in cold storage, not online (unless the site retired and you do not have an offline private key or wallet), nor any other wallet software. They can be used unlimited amount of times, so that's not the problem either. The problem your face is probably in Multibit. You can try to backup the .wallet or .key, and import it in another wallet software, or delete/reinstall Multibit.