Has to be a tough thing to do for artists who still tour a lot who had a history of prolific creativity.
All depends on the group and the circumstances.
There's bands like Iron Maiden, ACDC, and Metallica still releasing albums that are selling by the truckload and playing to audiences as big as they ever have regardless of what they choose to play (the old classics, new stuff or mix of both).
Then there are the acts who still release albums fairly regularly, still sell plenty of tickets, but it doesn't matter how good their new stuff is, (Bob Dylan, Bruce Springsteen, Alice Cooper etc.)all the fans generally want to hear is what they were playing 20-40 years ago.
Next are those that essentially reunite, don't need to record anything new, just turn up and play the old greatest hits set to sold out stadiums and everyone (fans, promoters and band) are happy.
I don't feel sympathy for acts that fall into any of the above. The ones I really have a lot of sympathy for are
Groups who have continued to write, record and tour high quality stuff, but for whatever reason are now playing pubs, casinos etc when in their glory days they were selling out stadiums and it doesn't matter what setlist they play nothing can change that.
Finally those performers who have lost the rights to the their band name and can't even sell tickets to a gig while other people are making a living performing songs the original performers wrote and are using the name of the band. Essentially the act now performing is basically a tribute band performing using the original band's name, while the former original members of the band can not perform under their name. The original members of Australian group Little River Band who achieved significant success in the US and Australia in the mid 70s through early 80s are currently going through this. Very, very sad. It's why didn't have any real sympathy for John Payne when Wetton, Downes, Howe and Palmer reformed. It would have been ludicrous if they had been unable to perform those songs using the word Asia in the band's title. I'm pretty sure they chose to perform as Original Asia simply to emphasise that they were the original lineup.