Board Flex

At what point(if ever)is the flex/pop no longer what it once was? To the point of needing a new board?

when it doesnt ride like it used to! lol

Dane has it right. If it flexes aot when you hit the wake, its not going to give you the pop. In other word, you've broken the rocker line. Eventually the edge will split and the core will crack. Its still ridable just not at the same performance level. (I'm refering to foam cores, have yet to do it to a one of these super exspensive cores)