This means nothing where Ross is concerned. Each players physiological development is different. Only the medical staff at FF know whether Ross is ready to play more football at the highest level.
Also, having the ability to play the game doesn't mean you have the physique, so the old "if your good enough, your old enough" shouts are worthless too.
When people talk about this league being the toughest they mean sprints undertaken, total distance covered, aerial challenges attempted and average HR amongst other things, not how heavy the tackles are or how many yard dogs are lurking at the back for Stoke.
For me he should play more because at times we desperately needed his creativity and burning him out won't mean jack for Everton as Bill will have him out the door once a big bid comes in.
But, if Ross was to start getting Rodwell type injuries because of overuse then I doubt his family,advisers would be singing Evertons praises and telling him to stick around either.