A band hanging it up is such a weird question. Unlike athletes, however, whose physical skills erode to a level that they simply overstay, musicians can still create music at the highest level if their passion for creating is there. Even a guy like Peart, who has retired, could still, after some practice, get into the studio and cut a record featuring a performance he'd be proud of. It was just the rigors of the road that was too much.
As fans, its difficult. For me, until Distance Over Time, I honestly thought DT was done, at least for me. I saw the I&W anniversary tour as a send-off to me as a fan. Go out with my favorite record from theirs, despite knowing it would be a challenge for JLB to pull off live. And it was, but I still had a good time. I thought that was it. But then I bought Distance Over Time, and was blown away, and equally blown away at the live show. I couldn't imagine them retiring at this point.
I hear ya -- leave on an up note. But what "up" is, could be entirely different to each person in the band, and all of us individually. So, no, I don't wish for them to retire, nor do I think they "need" to. But I hope, if a guy like JP decides he's done, whether that's tomorrow or 10 years from now, the guys don't try to "carry on."
Anyway, interesting thread, as I think it should be obvious to everyone that DT is most likely in the back half of their career. JP is 51, JLB is 55, and hell, JR is 62. Honestly, can JR stay on the road like this at 72? Can JLB still sing at a level befitting the DT catalog at 65? Other bands do it, but its rare that those bands really sound authentic, and DT's music is over-the-top complicated. So I think the thread and question is a fair one. I just think the answer isn't really yes/no.