OK, where's a band with roughly that kind of back catalogue, 30 years of career, that made their best work at the age of almost 50 ? Is there such an example ?
It's hard to think of a band making the best music of their career at that age, but they can still make
great albums. The one that springs most prominently to mind is Bob Dylan's
Time Out of Mind, which is a superb album made in 1997, fully
thirty two years after he made (in my opinion) the greatest album of all time,
Highway 61 Revisited (not forgetting the horrific albums that came in between from the mid-1970s to the late 1980s).
Time Out of Mind also had Daniel Lanois at the helm of course.
You might also add great albums recently by Bruce Springsteen or by lesser known individuals like Ry Cooder. And if you want a really left-field example, then look at a band like Tinariwen from Mali, who have only made two (superb) albums but only because 25 years in guerrilla training camps in Libya stunted their early career!
So the long answer is yes it is possible, however unlikely, for any artist to reach new heights at a later stage of their career. The one caveat I would add, however, is that it would probably take a reinvention of the art to do so, to move them beyond their natural comfort zone and into another area in which they can be challenged and - most importantly - inspired to make something that really speaks to them and pushes the limits of their artistic abilities. Then we might start thinking about art forms other than music and asking whether it is possible for
any artist to be at their height in their later days. Which, I would argue, it undoubtedly is - providing conditions are right and they find something that they think is worth writing about. (Which is where Eno and Lanois, Morocco, Fez and the different structure of the current U2 sessions - 2 weeks on/3 weeks off - come in).