The advice comes from England coach Andy Flower, who knows from his own experience that aches and pains almost inevitably begin to take their toll in the veteran years.
At 33, if he wants to continue being a 'long player' and one of a clutch of England cricketers engaged in all three international formats, Pietersen has to take great care over his physical well-being.
Flower puts him in the same bracket therefore not just as fellow 'thirtysomething' fast bowler James Anderson but Test and one-day international captain Alastair Cook too.
The latter is still comfortably in his 20s, but it seems he may yet be rested from certain engagements to ensure his longevity.
As for Pietersen, whose first-innings century was such a significant contribution to the rain-affected draw which helped the hosts retain the Ashes in Manchester on Monday, Flower said: "He'll have to look after himself as well as possible now, because he's in his early 30s.
"From experience, and talking to guys who have played at that age, everything seems to hurt a little bit more after long days in the field and after big innings."
Pietersen described himself as "an old man" after his hundred in Manchester, having been passed fit for the match at the last minute after a calf strain, and has missed three out of eight Tests this year because of injury.
Flower added: "The players that play all three forms of the game, we do try to look after in as wise a way as possible.
"Kevin's one of those guys, and in his early 30s, so we do take him out of certain competitions when it's necessary - just like we do with Jimmy Anderson, and might do with Alastair Cook in the future."
Flower's England have a default setting of refusing, generally, to look quite so far ahead as that - and the coach was predictably in that mode as he steadfastly considered only the next Test, starting at Chester-le-Street on Friday.
There was a hint, but no more, of the possibility of a rest for one of England's three pace-bowling incumbents - so hard worked in Australia's first innings at Emirates Old Trafford.
Chris Tremlett and Graham Onions have been included in a squad of 13, and Flower said: "We're totally focused on winning this series, and they are in the squad for a reason and available to play. We are quite willing to be flexible on that front."