I have a 2000 Byerly that I have ridden since it was new, and it has a lot of use on it. It is faded and has a lot of scrapes from sliders and bouy bonks, the rails have been repaired but are still true. I recently found a never ridden "leftover" of the same board on closeout, so I bought it, because I wondered if I would get more pop out of a board with a newer core. In actuality, I cannot tell a bit of difference between the two. I know very well that snowboard cores wear out and the boards loose their liveliness over time, but based on my experience with the Byerly boards, I do not believe this phenomenon holds true for foam core wakeboards, as my old beat up one still rides just as well as the brand new one.
It's just my experience, and I'm sure there are others who will want to disagree with me about this. I guess no matter what a person writes over the internet, there are always others out there wanting to disagree!