Hello, I play tennis usually as often as I can with school, which approaches 5 days/week. I got my racket for Christmas. I was wondering on whether to replace the strings now, or wait to re-string once a string actually breaks? Also, what kind of difference would I feel immediately after the re-stringing? When i'm playing tennis, I hear a solid clean sound coming from the strings when they hit a ball, and I don't hear that. Is it because I have old strings?