Have to agree that whilst bands can get away with changing drummers/bass players/guitarists , even if those players were a key part of their sound, to change the lead singer is a step too far. I don't particularly mind Queen with Adam Levine or when Paul Rogers was with them but I wouldn't pay to see them because neither come anywhere close to Freddie.

As for the classic older "heritage" acts there aren't too many I'd want to see now as vocalists especially can lose too much power/range etc (Tom Jones being a notable exception). Having said that, I would still see McCartney if I could as his shows still sound good even if his range has dropped and no mean feat to do a 2 and half hour show at his age. Think he has been playing with his current touring band longer than he did with the Beatles now.