I have had this problem with every set i buy. After about a week of playing, my stings have lost their punch, sustain and clarity and play badly. I use DR lo riders, or d'addario XLs (when the music shop has them). I am a teenager with limited funds so i cant justify forking out 80 bucks (AUD) for a set that lasts about a week. I have tried lots of things, like string cleaner liquid, boiling my strings and i wash my hands before i play, but nothing seems to work! HELP ME !