My two cents:
One of my favourite bands, The Cure hasn't released new music in the last 7 years, and for a long time, their albums were being released 4 years apart from each other (1992, 1996, 2000, 2004, 2008). So, I don't think anyone would say the band has been prolific in the last 25 years.
Plus, amongst fans and critics, none of the last 4 albums has been particularly praised, or at least not nearly to the same extent as their early output. Their so called 'masterpiece' was released in 1989. So, all in all, it would seem as if The Cure's peak is over.
Yet, for the last 4 years they have been touring many parts of the world, visiting places they hadn't for a long time (such as Hawaii and South America). They give long, long shows - a main set of 20+ songs, and another 15+ songs in the form of encores. In 2013, on Robert's birthday, they played 50 songs, over 4 hours. Their longest show ever, and (as far as I know) one of the longest rock shows by any band ever.
They've been touring for the last few months, playing a wide and interesting selection of hits, fan favourites, obscure b-sides and rarities, and 2 new songs. The setlist includes stuff from all of their discography. (They've played 80+ songs on this tour so far) They change the setlist constantly, every couple of shows, so each audience might experience something unique. (Pretty much what DT used to do until 2012) All in all, in my opinion, they work very hard and make it very interesting to fans and casual listeners.
So, I agree with Stadler - it depends on what you consider an artist's "peak". To me, The Cure is on a peak. They have no label or new release to support, yet they still tour the world over, playing a mix of everything, with great success.