But Kostner wasn't doing quads year in and year out leading up to Sochi. She wasn't even doing the lutz for a couple of years in there, or 3/3s either, due to injury. But she was competing every year, although not necessarily dominating. It's Chan's drive to dominate that will ultimately wear him out before 2018 if he continues to compete on a regular basis. And if he doesn't compete on a regular basis, then sporadic rigorous training can lead to injury (which happened to Lysacek and Cohen).
^^But the only person you've named that's a singles skater is Caro. (I'll add: Plush, Irina). Pairs/ice dance is a different matter.
In singles, 27 really isn't the ideal age. Especially since Chan appears to have already peaked (unlike Javi/Machida/Caro, who were late bloomers), and is already getting outclassed technically (unlike Plush and Irina when they competed at that age).
I'd be the last person to encourage anyone to retire the moment they peak, Ilia Kulik-style. I love it when the old-timers make it! (I've defended Aliona many times) But I'm just saying, there'll be no shame in Chan returning and getting no medal.
He's a beautiful skater to watch, and medal or none, it will be a treat to see him compete again. And if anything, it's commendable if he still wants to compete when the field will presumably have progressed. He must have been bored winning almost everything the past quadrennial, so it'll be nice to see how he stacks up with more of a challenge, now that his main competition has somewhat caught up to him artistically and are also themselves pushing the technical boundaries.
There are a few exceptions like Kostner, Slutskaya, Butyrskaya, and I guess you could sort of say Plushenko although he was a shadow of his former self when winning silver in 2010, but those are few and far between. Very few skaters in history, including even the ones particularly noted for their great longevity (Arakawa, Kwan, Boitano, Petrenko, Hamilton, Cohen, Kim, Yamaguchi, Kerrigan, Lysacek, etc...) were either still competing or competitive at the very top if they were still, at the amateur level. You cant say Browning either who at age 26 had an awful final amateur season. Nor would I say Takahashi who as you can see is no longer competitive technically for medals, let alone gold medals. The three women I referenced never stopped competing btw, which also aided their competitiveness at an advanced age. Never even took a break.
I didn't finish my thought when the pairs / dance took me away mentally. Yes to Butyrskaya, Irina, Plushy too.
And as others have pointed out: the quads alone would take their toll physically much, much sooner. How many surgeries has Zhenya had so far?!
^13? If we count the one he just underwent.
It's not just the active quad jumpers that have accumulated injuries though. Female skaters like Michelle and Yuna picked up a lot of injuries in their twenties (Michelle was only 25 when she retired. It's hard to believe it since she's been around so long, but I think staying at the top for so many years takes its toll).
We could blame Yuna's condition on the poor training facilities. That's what Plush credits his injuries to as well (perhaps the same for other Russian/Soviet skaters like Urmanov and Fadeev, who were also quite injury-ridden by the end of their runs). Patrick does seem to have avoided most of this, so perhaps he'll be okay. I guess, to be fair, it's not so much age itself that stops you, but the injuries you accumulate over time.
Also, it's difficult to stay on top for a long time. There are people who medalled at later ages (Caro, Evan, Paul Wylie, Shizuka, Maria), but they were rarely on top throughout their careers. They peaked later. I wouldn't say they're good analogies to Chan, who is closer to Irina and Plush in what he's attempting (if he goes for Pyeongchang). For a counter-example, you only have to look at the returning pros in Lillehammer...
My wish: Patrick compete at 2018 OG, and leave 2 clean programs. It does not matter whether he wins or not, as long as he is ranked high enough to enter the Gala, and Yuna will be invited to Gala (my dream) as well. Then they can hold hands and dance together for the last time. Then I can die in peace.
Patrick has not given any indication of skating in 2018. Four years is a fairly long time off. Much, I guess will depend on what comes along the next two years. He's going to Uni of Toronto (and I heard he's an Ontario scholar) and doing some show skating next few months. Perhaps the picture will be clearer in a year's time.