Former England captain Jamie Peacock believes he could play on into his 39th year but insists he will hang up his boots before then.
The ex-Bradford skipper, who turned 36 in December, has agreed a new two-year contract with Leeds which will take him to the end of 2015.
The front row forward has produced some of the best form of his career since stepping down from the international game in the summer of 2012 and says he is experiencing no signs of slowing up.
"I've never felt as strong and fit as this," said Peacock, who is 17 matches away from becoming only the fourth player in the summer era to reach 400 Super League appearances.
"Last year was the first time in over a decade that I had a full off season and I can feel the benefit of that again this winter as I look towards the new campaign.
"I still have a lot of goals I want to achieve in the next two seasons and high in those priorities is helping the transition of this group of players onto the next stage of their career and helping the Rhinos maintain the success we have had in recent years."
Peacock, who joined the Rhinos from Bradford in 2006, is the most successful player of the modern game, having won eight Super League titles and four World Club Challenge winners' medals.
Leeds coach Brian McDermott, who was a player at Bradford when Peacock made his Super League debut in 1999, believes he could play on beyond the length of his new contract.
"We'll have a look at the end of that contract and we'll see," McDermott said at the club's pre-season media day at Headingley.
"I'm not going to say 'no'. He's just in great nick. Whenever we do conditioning, JP's up there.
"He's incredible and he's not just a machine, mentally he's getting better and his influence over the group is immense.
"You'd put him up there, if not higher, than (former Australia and Fiji international) Petero Civoniceva with his standing in the game, He's one in a million. I don't think we'll get another one like him.
"I'm lucky to have him. He has an influence over the coaching side of things but I think JP has other things in his life. His desire is in administration. I think he wants to take over the world."
Peacock is currently studying, alongside Leeds captain Kevin Sinfield, for a masters degree in sports administration and will hang up his boots at the end of the 2015 season even if he feels he could continue.
"I think I probably could but at some point you need to call time and move on with the next part of my life," he said.
"I think it's good to have a goal of where I'm going to finish and it's good for Mac to be able to plan for that.
"I'm driven in what I do. I've had a successful rugby career so far and this will take me through to 20 years as a professional player.
"That will be it and I've then got 20 to 25 years working and I want to be successful at what I do then.
"I think I would enjoy coaching but it's not top of my list. When it gets to the second half of 2015, I'm going to start looking for work. I would particularly like to get into senior management in sport or the media."
Sinfield welcomed Peacock's decision to play on, saying: "To get to be able to play with him again for another 24 months is fantastic.
"He's a modern-great. He's one of the legends of our sport and to have him here for the vast majority of his career is fantastic."