Are all Pu-erh teas the older the better?

It is well understood among the Pu-erh tea drinkers now that the older a Pu-erh tea is, the better the quality.  

Like many other foods that maturity is part of their quality however, such as red wines, they have also all got their quality peak, some are right now and others are way in the future, especially for a plant product such as Pu-erh tea. Once the peak has been reached and past, the quality will start deteriorating.

An example of this is that some pu-erh teas (can be of any age) that are first sweet and aromatic, but become flat and plain with time.