First off, Oda is not old, he's not in his 80s or 90s.
Second, as much as many don't like him working on the live action, that's what he chooses to do.
He doesn't have to do it, but he wants to do it because he wants really wants to the live action to go smoothly.
Some people here act like they know what is best for Oda, but here is the thing, we don't know Oda personally, we are not friends with him, and we don't work alongside him.
Does it suck that he is working on the live action and that delays the manga, yeah it does but again that is what he chooses to do and what he wants to do.
And again Oda is 49, he's not that old, as long as he doesn't have any severe health problems he should be fine, the manga isn't going away anytime soon.
Instead of complaining about the manga being on hiatus again, read or watch other series or do something else.
As much as I love One Piece, there are plenty of other great series out there as well.