Rio Ferdinand and Nemanja Vidic are enjoying a new lease on life at Manchester United.
And after a summer of change at Old Trafford, they're proving some things are better left well alone.
Injury—to Vidic mostly—and competition from Jonny Evans meant Ferdinand and Vidic were only paired together nine times last season.
With the emergence of younger players like Evans, Phil Jones and Chris Smalling, it could have been seen as the beginning of the end for a partnership which has won 11 Premier League titles between them.
With a combined age of 65, even the best things must end sometime.
But those penning obituaries for one of the finest central defensive partnerships the club has seen—alongside Steve Bruce and Gary Pallister and Ronny Johnsen and Jaap Stam—have been forced to pause.
Are Ferdinand and Vidic Man United's best centre-back pairing?
David Moyes has had his problems since taking over from Sir Alex Ferguson this summer. But his defence hasn't been one of them.
Vidic and Ferdinand have started every game.
Wilfried Bony and Daniel Sturridge are the only players to find a way through.
Their run can't go on forever.
They're both now senior statesmen, and creaking bodies need to be managed in a way that gets as much football out of them as possible.
Vidic has had trouble with his knees in the past, Ferdinand with his back.
In that sense, Moyes is lucky to have such able deputies.
Evans played 30 games last season and was trusted to look after Cristiano Ronaldo, Karim Benzema and the rest in the Santiago Bernabeu.
And he would have had more opportunity to break up the Vidic-Ferdinand partnership this season had he not picked up an ankle injury during preseason.
Jones and Smalling have got a long way to go before they can boast the experience of Vidic and Ferdinand, but both are England internationals and capable replacements.
Even young Tom Thorpe, a former England Under-19 captain, and Michael Keane will be knocking on the door soon enough.
But even with fierce competition for places, Moyes has shown that Ferdinand and Vidic are his preferred pair.
That doesn't mean they'll play every game. Their age wouldn't allow it.
They've got more than 700 United games under their collective belt. And they're proving they've got a few more left in them yet.