I've read that the bond between the fibers in our composite racquets can break down over time giving the frame a "dead" response...high initial flex, but no rebound. Has anyone noticed any practical difference in frames they have played with for years? I've got a Head PT280 I've used on and off for over 10 yrs. I've been trying some new and re-issued players frames of similar flex and noticed the old PT280 seems to have a somewhat "dead" response in comparison. Never seen this topic discussed... Think this is real or BS?