I always read "drink between now and .."

[MontereyRick]

I consider myself a real fan of wine, know what kind of wine I like and what kinds I don't and have a wine cellar with around 450 bottles..

Problem is, I'm just not very good at explaining which characteristics it was in a certain wine that I either liked or disliked..I rarely spend more than $20 a bottle because I feel anyone can spend a bunch of money and find very good wine (everyone's tastes being different, of course); but more fun is had in buying wine under $20 that people think tastes like a $50 bottle. I have learned that buying decent Cabs or Zins and cellaring them for a couple years helps a lot. However, I always seem to read that some experts opinion is that a certain wine should be drank "up until 2005", or drink "between now and 2009" or will "be best in a couple of years".

Here is my question:
Why is it one wine may continue to get better up until 2009 and another similarly priced, same varietal may only get better for another 2 years?

Do some red wine not get better at all?