It's a fact that polyester resin gradually loses its memory with each flex.  So, boards that get used frequently will die long before ones that sit around. 
I know of no scientific study that could tell you exactly how many flexes it takes to kill a board.  There are just too many shapes, thicknesses and lengths to do this.  Typically boards die at the same time all over; dings, scratches, fading and flex.  By the time a board is this far gone it is time to invest in a new one.

Last Edited By: Rich Harbour Jan 13 11 10:05 AM. Edited 1 times.