Age def has it's effects on one's voice, and so will it have on Chester's. It's an undeniable fact. However, with different techniques, I'm sure he's still pretty much able to pull everything he did before off. Listening to Crawling in 2010 compared to 2000, he does the exact same notes, but gives it more a classic approach, rather than his raw voice he used to use. Btw, 2007 => Given Up. Wouldn't really call that "weakened", so mainly it's people who dislike the new direction the band is going, and the new use of Chester's voice that fuel the opinions.