The great athletes of every era get more interesting as they get older, and the magic gets harder to summon.
So it is with Roger Federer.
He shrugged off his 30th birthday last month by saying: "It's just a number that's changed."
But he knows it is hardly the only thing that has changed for the greatest tennis player ever.
The victories do not come as often as they used to — Federer has not won a major title in 18 months — and the questions have changed, too.
Before the emergence of Rafael Nadal, Federer often was asked whether he would ever find a worthy rival.
Now, at the close of a sensational run that has enabled Novak Djokovic to leapfrog past him as well, Federer gets asked how much longer - sometimes even whether - he can hold up his end of either rivalry.
One other thing appears to have changed, too: the pride that always simmered beneath that smooth Swiss veneer is bubbling to the surface on occasions.
More than once over the summer, Federer reminded a questioner that he knows the history of 30-something stars in grand slam events (only five wins in the last 100) better than those who bring it up, not to mention the balancing act required to stay at the top of the game with two-year-old twins at home.
He did not go John McEnroe on any of his interviewers, but he did set one or two straight, occasionally slipping sarcasm into the mix.
For a champion whose public demeanour always screamed vanilla, that qualifies as progress.
Nobody who holds the record for major championships in his chosen field does it without a supersized ego. So one of the most remarkable things about Federer is how skilfully he has masked his all along.
Instead of seething, he dutifully managed it one more time at the US Open when the line of questioning veered toward his age.
"I'm still as professional. I'm still as hungry," Federer said at one point. "I feel my game allows me to still play for many more years because I have a relaxing playing style."
But Djokovic, the defending champion, gave a more expansive and honest answer to a similar question.
Asked whether he could see Federer and Nadal reprising their battles for No 1, and pushing him back to third, Djokovic said: "From all of us, [Federer] knows the best how it is to win the major events ...
"He has 16 grand slams, has a fantastic career, and so I'm sure he wants to come back there."
As far as motivation for Federer, there is that No 1 ranking to reclaim, a chance to close the gap on Nadal (who holds a 6-2 edge in grand slam final meetings), and the few major records he does not already own.
If those don't do it for him, well, there's always the critics.
But Andre Agassi, who won the Australian Open in 2001 and 2003 - at 30 years old and 32, respectively - noted that Federer never really needed pushing, not when he had no real rival and even now that he has picked up two capable of standing up to his best.
Earlier this summer, right after Federer broke Djokovic's 43-0 streak in a French Open semi-final and prepared to play Nadal, Agassi said: "I've always been a different cat as it relates to motivations and reasons for playing, reasons for digging deep, reasons for continuing.
"Roger, I don't know if he's just that good mentally or he's so talented that he can just get away with it.
"You would think one would lose that edge mentally, and certainly physically. But what he's doing, again, I can't give him enough credit. I don't know how you continue it, but he looks like he's not stopping in the near future."
Not the near future, certainly, but the end of Federer's reign, if not complete by now, is coming into view.
During the same conversation, Agassi marvelled, "I'm thinking this guy can do this for another five, 10 years," then caught himself. "Not 10. I'll actually make that prediction. Ten is probably too much."
At this point, all Federer is concerned with is winning the US Open.
In reflective moments, he has acknowledged the changing nature of the game, and the pressure exerted by younger lions such as Nadal and Djokovic, have made it tougher to hang on, and he does not see himself as a "special case," able to defy time and tide.
But there is no question he was once, and could be again, especially if he is determined not to go into the night quietly.