Today’s tennis fans are spoiled. They have watched Serena Williams, Venus Williams, Roger Federer and Rafael Nadal, four of the best tennis players of all time, dominate the sport for a decade, winning a combined total of 60 majors in their careers. Now the four are old by the sport’s historical standards — all are at least 30, and only Nadal is under 35 — but instead of fading away like their predecessors, they’ve dragged the sport along with them. This weekend’s Australian Open finals are Grand Slam showcases of their longevity: Williams vs. Williams IX on Saturday and Federer vs. Nadal IX on Sunday.

The mid-30s is past closing time for most tennis greats, and all four have declined. Combined they’ve won just one title at the last five majors. But they’ve remained remarkably competitive, regularly beating their younger peers and threatening to go all the way once more. Two of them will do so this weekend. Federer and Nadal benefited from early exits by No. 1 Andy Murray and No. 2 Novak Djokovic but also knocked out five of the top 10 seeds themselves. The Williams sisters had easier paths to the final, after many of their inconsistent younger rivals lost early. All four have looked like their best selves for long stretches at this tournament, outplaying and outlasting younger opponents.

Now Serena Williams will go for an Open-era record 23rd major title, while Venus will seek her eighth, and her first since 2008. Federer will try to extend his lead over Nadal in the career major title count to four; Nadal will try to narrow it to two.

By historical standards, what Nadal is doing is remarkable; what the other three are doing is almost unheard of. Federer is the oldest men’s Grand Slam finalist since Ken Rosewall more than 40 years ago. Whichever Williams sister wins will be the oldest woman to do so in the Open era, surpassing Serena’s record, first set at Wimbledon in 2015 and extended in last year’s Wimbledon.

How are they defying the laws of aging? Partly, the sport has aged around them. Veterans have gotten smarter about diet, conditioning, practice and scheduling. Their biggest rivals (Angelique Kerber, Maria Sharapova, Murray and Djokovic) are themselves 29. None of them made the semifinals in Australia (Sharapova is serving a doping suspension that ends in April), but two of the other four players who did are in their 30s; the other two are 25. The next generation of players hasn’t broken through.

But in large part, the four greats are the reason tennis has aged. When they were young, they dominated, and tennis seemed young. Now they’re old — and tennis is, too. All-time greats, even after they’ve been diminished by age, often remain great, as did Peyton Manning, Wilt Chamberlain and Hank Aaron. Tennis’s oldsters remain four of the main faces of the sport. Federer by himself has accomplished about as much at majors since turning 32 as has every man 27 and younger combined. By contrast, the average age of men’s major semifinalists was under 27 each year from 1987 to 2011.

Andy Roddick provides an instructive contrast. He’s a year younger than Federer and has 16 fewer Grand Slams, yet he retired more than four years ago, unable to continue competing at the very top of the sport. At a press conference in Australia this week about his induction into the sport’s hall of fame, Roddick marveled that his peers were still going. “What Roger’s doing and maintaining at 35 years old, what Venus and Serena are still doing …,” Roddick said. “Everyone here is going to talk about it in every story they write for the rest of this tournament, and I still don’t know if that’s enough. It’s pretty amazing.”

There’s no guarantee that this will last. No one can spot the last hurrah in advance. Rod Laver won all four majors in 1969, the year he turned 31 — and then never reached another major semifinal. Andre Agassi, at age 35, led Federer in the 2005 U.S. Open final and then never reached another major fourth round and retired a year later. Martina Navratilova reached the 1994 Wimbledon final at age 37 and then played just two more majors in a brief comeback bid a decade later. But there isn’t much sense in writing off any of this weekend’s finalists. Others have done so before and turned out to be way premature.

After clinching her spot in the final, Venus Williams said aging has been good for the sport, which gets to keep its headliners headlining finals for longer. “I think people realize this is an amazing job, so it’s best to keep it,” she said at a press conference. “I think this generation is going to inspire the rest of the generations to, obviously, play a schedule that’s achievable, sustainable, and that you can play Grand Slam tennis for a long time. This is beautiful for the game because it will be able to retain its stars for a long time, which is a great business model.” After all, no matchups are easier to market than Williams vs. Williams and Federer vs. Nadal.