Bono's voice has got worned out

[silvrlvr]

Singing high notes in and of themselves does not damage your voice.

But you have to be in good voice to hit them, and if you drink/smoke/generally carouse/are on airplanes constantly/and don't get enough sleep, you won't be. The vocal cords depend on good hydration, for one thing.

Singing is as physical as any sport, and singers in top condition sound better just as athletes in top condition perform at their best.