Okay mate I see your point.
But he lost his ability to play a box-to-box role around 2010 mate (at the age of 29) - remember that World Cup game vs Germany?
Since then he's slotted to a holding midfield role and his ability to read the game, and like you said, done it very well - helping City to trophies in the meantime and doing so for six years now.
As long as he has an 'energy' player around him, we're fine.
Also, doesn't Barry have like the second-highest running (distance covered) stats in the league and wasn't that same last season as well?
So, even with his age, no signs that he's clearly lost his ability to cover ground in the position he needs to.