There are a couple of issues that raise their heads when it comes to getting the band back together, though. One obvious point is That's fine if you've managed to tweak your lifestyle circumstances so you can get by on a minimal income. You mightn't be able to manage that if, for example you have extensive alimony commitments, ongoing family health issues or a large dangling mortgage.
On the other hand, if you're a musician who doesn't write, or don't write prolifically enough to maintain the sort of cycle that Costello, Cummings, Thompson and Young manage to churn out you've got a problem, even if there's a back catalogue to draw from.
That's exacerbated if you don't have the sort of name recognition that allows those four to sell out a reasonably sized venue, which brings us to the issue of when a name act ceases to be an entity that can use that particular moniker.
In some cases that question is academic. You were never going to see anyone going out as The Beatles without the presence of all four of Messrs Lennon, McCartney, Harrison and Starr, and for each of those gentlemen there's enough name recognition to allow them to generate enough to get by without having to.
Then there are the obvious examples like The Rolling Stones and The Who, where a line up that didn't include both of Jagger and Richards or Daltrey and Townshend would be laughable. The matter of whether anyone should bother to go, of course, is another matter entirely, but if you went to a Who gig you'd be expecting a bit of Townshend arm-flailing and Daltrey microphone twirling along with a set list that included most of the classic Who tracks.
In the same way, anything that doesn't have Mr Jagger strutting out the front and Keef churning out the riffs ain't gonna be the Rolling Stones. Whether you'd actually want to see them go through the motions in a stadium, effectively watching what's happening on stage from the next suburb is an entirely different kettle of fish.