What is the fine-grained topic of the following text: Forget all the nonsense about Merlot producing sweet, soft, ready to drink wines, because low yielding, old Merlot vines made in the way of Petrus and other top Pomerols frequently possess as much aging potential as any great Cabernet Sauvignon-based wine in the world. Only return the topic.
The aging potential of Merlot wines