DAYTONA BEACH, Fla. (AP) — Jeff Gordon is working in the broadcast booth. Carl Edwards is spending time with family. Tony Stewart is hanging out at dirt tracks.

Some of NASCAR's biggest stars have stepped away over the last 15 months, a thought-provoking trend that doesn't appear to be ending anytime soon.

Gordon (2015) and Stewart (2016) retired from full-time racing in consecutive years, walking away with a combined seven championships. Edwards called it quits last month, abruptly leaving before the final year of his contract with Joe Gibbs Racing. Edwards said his decision was personal and private. What made it so bizarre is that Edwards was 10 laps away from winning his first championship just two months earlier.

Even if Edwards returns to the series next year, it probably won't do much to stop NASCAR's ongoing face-lift.

"When I first started watching the (Washington) Redskins, a lot of wide receivers and cornerbacks were playing into their mid-30s regularly and now they're not," NASCAR star Dale Earnhardt Jr. told The Associated Press this week. "Nowadays, at 30, they're starting to look for somebody else and wondering how much more mileage they got on them.

"I think we're seeing that in NASCAR as well."

Other aspects of the issue, Earnhardt said, include drivers starting racing careers much younger than ever and the constant demands on those who reach NASCAR's pinnacle, the Monster Energy Cup Series.

Earnhardt estimated about 90 sponsor or team commitments during the series' 36-race schedule, leaving little room for downtime, family time or me time.

"Back in the 70s and 80s, when guys were racing into their 50s, they were running 28 races and had a lot of time off," he said. "They didn't have sponsor responsibilities. Ninety days of work off the track? What was Bobby Allison doing in '83 with Miller? Twelve days off the track, maybe? They had a lot of time to do what they wanted to do to unplug and keep their battery charged."

Throw in escalating salaries over the last two decades, and it should be no surprise to see drivers choosing a less-stressful lifestyle — even with safety advancements making the sport seemingly as safe as possible.

Michael Waltrip, a 53-year-old former team owner/driver who has raced a part-time schedule since 2009, is making his final NASCAR start in the season-opening Daytona 500 on Sunday. Veteran driver Greg Biffle, 47, announced last week that he won't race full time in 2017. Biffle accepted a recurring role as a guest analyst on NBC Sports' "NASCAR America" show.

Others might soon join them on the outside looking in.

So who could be NASCAR's next retiree? Here's a look:

EARNHARDT: The 42-year-old Earnhardt missed 18 races last season because of what he believed to be his fifth documented concussion. NASCAR's most popular driver was cleared in December to return to racing, but acknowledged this week that he would consider retiring if he won his first Cup championship in his 18th season.

"It'd be hard not to spike the football on stage in Vegas and call it a career," he said. "Why not? There's still a lot about it that I haven't done just the way I want to do it. I want to learn how to enjoy it all the way, fully. I've got a couple more years that I'd like to keep going.

"But, dang, yeah, if I won a championship, shoot, that's the motivation for me in competing. Once that's checked off the list, that'd be everything."

MATT KENSETH: At 44, Kenseth is the oldest full-time driver left in the Cup series and he's entering the final year of his contract at Joe Gibbs Racing, which has talented youngster Erik Jones waiting in the wings.

"I don't know exactly how it happens or if you roll over one day and wake up and are like, 'Man, I don't want to do this anymore.' Or you stink and can't keep a ride," Kenseth said. "I will say: I feel really good right now. I think we're pretty competitive. I love the guys I'm working with. I love my race team. I don't have any plans to do anything different in the foreseeable future.

"But you never know when you're on your last lap or last race, necessarily. I certainly don't have a plan on the horizon when I want my last race or last year to be. I still feel like I'm a ways away from it."

JIMMIE JOHNSON: Coming off his seventh NASCAR title, the 41-year-old Johnson has started spending more and more of his spare time in Aspen, Colorado. An eighth title would push Johnson past Dale Earnhardt and Richard Petty for the most ever, leaving him alone as NASCAR's greatest. Could that also lead him into retirement?

"I'm more concerned about when the fire goes out," Johnson said. "And I'll use Mark Martin as an example. It was four, five, six times he tried to walk away and the fire was still there and he came back. In talking to Mark, he really missed it. He wasn't at peace out of the car.

"I want to do it when the time is right. If I start thinking about my safety and concerned about injury, it's time. I've always been very aware of that."

DANICA PATRICK: At 34, Patrick would seem like a long shot to walk away after this season. But with no top-five finishes in 154 races in four full Cup seasons and now sponsorship concerns, it's unclear how much longer Patrick will have a ride at Stewart-Haas Racing. She admittedly wants a family, is working on fitness book and has built a brand as strong as anyone's in auto racing.

"I understand how it hasn't really, result-wise, progressed a lot," Patrick said. "In fact, it's regressed. So why is that? Am I worse driver than I was a couple of years ago? Probably not. I don't think anybody gets worse. So it's really a matter of all the factors around you, whether it's cars or a new crew chief or new personnel or just and luck that year.

"There's just ebbs and flows to it all, and let's hope we're on the upward flow."

OTHERS: Kevin Harvick, 41, Jamie McMurray, 40, Ryan Newman, 39, and Kurt Busch, 38, could be in the twilight of their careers, especially with so many youngsters clamoring for rides.

"These guys are racing cars at 5 years old and competing hard and getting competitive," Earnhardt said. "Racing weekly in any rank is a challenge, even the local guys. To do it at 16, 17, is tough. And, man, when you're taking a 5-year-old to the race track every week. Is he going to race from 5 to 45? At some point, they're going to go, 'I think I want to do something else. I've raced a lot. I think I've raced enough.'

"So I'm not surprised by these guys retiring at 42, 43. There are a lot of reasons for that."

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