Hey, YouTube is only trying to be helpful! It knows that a half-life of a video is about 5 years - every YT video will eventually decay into error message, via one of many phenomena identified by experimental SaaSysicists, such as "geo-block decay" (and its special form, "Germany block decay"), "spontaneous demonetization", "spurious content-ID block", "channel-ban induced cascade", or "Decay Measurement Cascade Anomaly" aka. "DMCA". So it really just wants to make sure you'll watch the video before it's too late!