I've had this discussion with others before, & hold the distinct minority view that Classic Rock has more to do with a
style of music than it does with any strict chronology or year of production.
In other words, the new Black Label Society is certainly not Classic Rock. It may be Metal, but there is a lack of distinct melodies & memorable chord progressions. It may be the sound of 2006, but it has little to do with the song structures of, say, early Black Sabbath or Zep or Humble Pie.
However, I think the relatively new Collective Soul cd/dvd "Home" recorded with the Altanta Youth Orchestra falls completely within the Classic Rock style or category, even tho it was only recorded & released in the last year.
I could see a guy like John Fogerty being completely comfortable sitting in or recording any of CS's songs, because they are very in a similar Classic Rock style as his work with Credence Clearwater Revival.
I don't subscribe to the idea that a song or band has to be of a certain age before it can be considered Classic Rock.
I think it's more important for the work of art to embrace certain musical & production techniques or styles. That's how I tend to categorize music, more than what chronological era it was composed in.