I have some wilson enduro pro strung in my racquet that is about a month to two months old. I can still hit decent shots with it and play, but it just doesn't feel as crisp and nice as say week one or two. But now, it has developed a slight pingy sound when i bounce the ball on the frame a bit, i'm wondering if thats because the polyester has lost tension, or something with the racquet? Would you expect this kinda thing to happen with old strings? It almost feels like my racquet has no dampener and "pings" but of course my dampener is still there.