Well, smoking clearly punishes many voices - look at Joni Mitchell. It's truly painful to see what smoking has done to her. Then again, Lou Reed's been smoking pretty much non-stop all his life, and whatever you think of his singing voice, it's as clear and as strong as it ever was.
(Bob Dylan's deterioration is something else again. While smoking has surely contributed (he's never stopped the cigs and added cigars in recent years), there seems to be something more to it.)
As for drinking, drugs, etc - all of it can have adverse effect. It matters what you drink and how much. Beer is extremely rough on the throat and singers should steer clear of it before/during a performance. Brandy and kosher (sweet) wine, on the other hand, help keep the throat warm and moist.
Oh - constant touring/performing shouldn't, in and of itself, take too harsh a toll on the voice, IF you know what you're doing. But that's a problem for many rock singers, it seems.
Judging by the live recordings from the last couple of years that I've heard, Shane's voice is still in pretty good shape. No, he doesn't have the incredible voice of his youth, but it still sounds good to these ears.

