I have not kept up with Iron Maiden since Brave New World, which I now realize was 23 years ago, but it really is sad to hear that they are growing too old too keep up with their music. My personal favorite, in terms of (power) metal, Blind Guardian, should be safe for a while yet. They are a tad younger, but also creeping up on sixty by now.
As for Peter Cornelius, his arrangements are not the most complex, so unless he eventually develops arthritis like Ritchie Blackmoore, he will probably be good enough to keep playing for a while yet. His voice is the bigger problem, he always had lung problems and even as a young man and had to undergo long bouts of therapy during his career as part of the German Hair ensemble - and that was before he became a heavy smoker.
He also had a bout of burn out where his doctor prescribed him, to quote, "any- and everything he could without risking the loss of his approbation (German medical license)", which lead to an episode of paranoia and weird interviews about conspiracy theories. At least he is still alive, which cannot be said for some other local artists that I enjoyed who began their carreers in the late seventies. A heavy smoker who died of lung cancer back in 2007 and one who died of a heroine overdose in his early thirties. Then there are the others ruined by alcohol, hollow shells of their former selves.
I generally do not post any of their music here because it does not make much sense to do so: they are and were all gifted songwriters, but there is barely any appeal for anyone who does not understand the language, and even then, well, one would need a certain cultural understanding to truly appreciate the lyrics*. The music of Peter Cornelius is somewhat different, like I said, it is maybe possible to enjoy his music even without understanding a word.
The guy who died of an overdose could have had a pretty good carreer, even internationally.
Alas.
*In case anyone's interested. Put in spoiler tags as this post is long enough already.