For The Love Of Port

One thing I APPRECIATE about Madeira over a tawny port, for example, is its LONGEVITY once open.

It seems,though, here and there, as I've read TNs, that some of the Madeiras DON'T LAST as long as other Madeiras once open.

Reason or rhyme for this?

Unless you point out the actual examples, I have to say that I don't understand. I know nothing that would qualify one Madeira to have more shelf life once opened vs. another. That being said, I would "guess" that the longer in wood, the more stability the wine would have and for Madeira, that would have to lead to some better quality of life once the cork is pulled.