Depends. Media links could become dead if the file is deleted from the hosting server. A link to Giphy might break or even point to a different image without you knowing. But a link which includes the hash of the image, like nostr.build or blossom based servers, encodes the actual image hash, so even though the link doesn’t change, a client can potentially look on different servers in the case of a dead link because it can prove the image correct because of the hash.