Interestingly, this past Thanksgiving I bought a bottle of $25 red wine of French burgundy instead of the usual $10 bottle, thinking I'd splurge a little this year ... (yes, we're OK with French wine again:) ... anyway, we didn't finish the bottle, so there was some left over at Christmas. Upon tasting it at Christmas dinner, it was BLAAAHHHHHH (spiting it out) .... turned *really* sour, so poured the rest of it down the drain and opened up a new bottle of a 'different' $25 chardonnay, which we enjoyed (and finished off this time, wasn't going to let the same thing happen again! /laughs)
Anyway, the moral of this story is that the previous $10 red wines still held their own a month later, given the same circumstances, than than the 'splurged for' $25 bottle.
I try not to be a wine snob, but I must say that opening a bottle of ANY wine and expecting it to be drinkable a month later is ridiculous. (Port, sherry, madeira, and other sweet fortified wines are the only exceptions.)
Wine is destroyed by exposure to oxygen, and I have seldom tasted an opened bottle that was worth drinking even a week later.
-ccm