Erm who are we to say he should quit smoking??? Thats his choice, also, Iv said it before, but loads of brilliant singers smoked all thier lives. You can't be sure that smoking has made any difference to his voice.

btw before anyone jumps on me I'm not saying I havnt noticed a change in Jons voice, it has got weaker but for all we know jon could be "working" on his voice everyday, there may be nothing he can do about it.