This classification doesn't replace individual wine reviews or scores. Every vintage from every producer – ten-star or otherwise – is still tasted and judged on its own. A ten-star winery can make an average wine in an average year, and that wine will be reviewed as such.
Nor is status permanent. New ownership, a change in style, or a run of underwhelming releases can lower a producer's rank, just as a sustained run of excellence can raise it.