Their problem - and it's sort of a serious one, IMO: how to make a bunch of middle-aged guys with a reputation as 'miserable bastards' suddenly appear to be more fun than a barrel of monkeys...without making them look like ridiculous stereotypes of 'rock stars in mid-life crisis' (AKA David Lee Roth, etc). Very tricky.
On the other hand, they don't have to record one more song if they don't feel like it, and if they still enjoy the whole recording music thing, they can afford not to be successful, so it's only a PR problem if they're still interested in the "biggest band in the world" gig.
Well, of course - at least in a way. I presumed that went without saying, given that at this point, they have More Money Than God.
But what I have discovered with a lot of these bands with a conscience (and U2 is at the very top of that list) is that they care very deeply about their legacy. At least that is the case with two of my favorite bands who also have places on that list - Springsteen and Pearl Jam.
When you have a conscience...and have sought to use your fame for good on the level that these kinds of bands have, it's no longer about money. Any of these guys could quit tomorrow and be set for 3 lifetimes. But it's not about that.
I can't speak for U2 since as I just stated, I have not watched any documentaries about them/interviews with them in a VERY long time. But I am pretty knowledgeable about Springsteen and Pearl Jam. And I can tell you that for both of them, it's now about 2 things:
1. Continuing to be creative is still fun for them personally (this is something you can do without being 'big', of course); and
2. They want to leave a legacy that will be respected. And this means both musically,
and as Citizens Of The World. I think that in the case of all 3 bands, their body of work speaks for itself and the 'musically' part is take care of, but the Citizens Of The World bit? - continuing to do good and speak out for what is right on the level they have - that takes 'being big'...or at least 'being relevant to a lot of people'.
As I said, I don't follow U2 much any more (in fact, just yesterday I actually got annoyed when XM Radio station Lithium (supposedly devoted to grunge) played a U2 song when I was in the car - I remember grumbling "U2 isn't fucking grunge!", as I turned the dial in mild annoyance

)...but one thing I have always taken away from Bono is that he wants to use his street cred for good. And it's VERY important to him - not just a 'hobby' when it's 'convenient'. I deeply admire him for that, because I know more fully what things like taking a stand against Dubya has cost Springsteen (and Pearl Jam, for that matter).
So I think that U2, while they could easily just 'not care' if they were big anymore, might struggle with the notion of 'just hanging out and playing a few clubs'. Not because they need the money....or even because they crave the fame for it's own sake (neither of which I believe to be the case)....but because they need that international platform to continue to spread their 'citizen of the world' message.
I think it means something to them. It certainly would mean something to me, if I were in their place.
That's why I think U2's situation is particularly tricky. Because their version & tone of the 'citizen of the world' message is part of the reason they have acquired that rep as 'miserable bastards'.
Just my take from a (now) U2 outsider who used to follow them a lot more seriously. Your mileage may vary, of course.
