That would make more sense if we were talking about an athlete.
Oda is only becoming more skilled, being able to draw and write better and faster, the more he acquires experience drawing and writing his manga.
Until he gets really too old, like 70 years old, and is actually sick, getting older just means he's getting more capable of drawing and writing the manga. So I don't see any reason to think he should take more breaks; On the contrary, it's better if he makes good use the age he has now, in which he has accumulated a lot of experience and isn't too old to be sick almost dying, to draw and write as much as possible, instead of slacking off taking a lot of time to draw each chapter and then ending up like Miura, never being able to finish his manga.