This is the precies message Oda wrote to all of his fans last year, that appeared in Shonen jump as a way of explaining his absence.
It goes at following.
I messed up!
I put up with my illness for too long, and my condition got worse. I apologize to all the readers who were looking forward to the next chapters, as well as to all the Straw Hats who were really looking forward to wreaking some havoc. But I'm currently going through some painful treatment. The story was just about to take a new turn, so I really really wanted you all to read the next chapter as soon as possible. I know how long two weeks can feel for all the shonen out there, but please wait for just a bit longer.
— Eiichiro Oda
So what can we learn from this? Oda is deeply dedicated to his work, and cares about his fans a lot.
And I think it's important to keep in mind.. he doesn't even have to. One Piece is the single most popular manga in japan, if he decided to take one years break, shonen jump would still be ready to welcome him back with open arms.
Though, if he decided just to stop.. right here and now, he could do that to. He earns 25 mio dollars in just royalty, every single year these days.
The only thing keeping him going at a rate so quick that it's health risking is indeed.. His dedication, his love for his manga, his love for his fans.. He lifes just to put that manga out.. so yeah.
Sorry I called you out to, I am not actually mad.. I get that for consumers it gets hard, even near possible to even imagine just how much works goes into what you consume.
That is indeed the irony of an artist, you work and work and work so hard to make some-thing, and it's consumed by the consumed in minutes, then they go home and think nothing more about it. it's that way in ALL entertainment media.. it takes a heck of a lot less afford to consume than to create.