Not saying you're wrong, but I'd like to see a study on this known scientific fact. I've heard different opinions on this from different people. For me personally, I've used racquets as an active junior for well over several years without noticing deterioration of playability. I also almost never restring unless I break the strings, which was more frequent with those Prince synthetic gut strings (with Duraflex!) I used back in the day. Now I play mostly with 16 gauge poly strung at 53 lbs. I've been hitting frequently (often against the wall, which wears down strings even faster) for a month, and the strings are still playable. In fact, because I strung them on the tighter end of the spectrum to begin with, they feel better now than when they were new. If you notice the frame becoming softer after a year or two, perhaps it's because you're stringing your frames so frequently. There's evidence that the stringing process puts more stress on the racquets than repeated hitting would; I seem to recall that Kuerten enjoyed a softer frame and would string his racquets several times at high tension before actually playing with them.This is known scientific fact.