From what I've seen if the domain is down and the nostr.config file containing the userhandle and pubkey doesn't load, then the 'verified' symbol currently goes away. This would mean having to re-verify using another provider or self-verify using your own domain I guess.

If the domain or server went down today, your NIP-05 ID would stop working. Thankfully, I plan to run this forever or until nostr dies. The domain was only bought for one year, but I plan on renewing every year for the foreseeable future. I have big plans for this. I gotchu.