I think this makes sense, but I think it's also important to not equate "earning out the advance" with "profitable to the publisher". The advance is one of the expenses of publishing a book, for sure, but it's not based on the break-even point for the publisher. It's quite possible for a book to not earn out its advance and still make a profit for the publisher. They might not offer such a large advance the next time around because they don't need to, but that doesn't mean they're actually losing money.
Depends how long it takes you to write a book. At one book a year, 15% going to the agent, and probably some author expenses, it's not that much money. I mean, I wouldn't complain, but I'd still definitely care about my royalties! And still probably keep my day job...
Well, I make little money as it is. Anything about 25 grand would allow me to live better than I do now I'd just take a year off to write and take it easy and see whether I can crank out another book.
Hmm, reminds me of this extract: “The press is a gang of cruel ******s. Journalism is not a profession or a trade. It is a cheap catch-all for f***offs and misfits--a false doorway to the backside of life, a filthy piss-ridden little hole nailed off by the building inspector, but just deep enough for a wino to curl up from the sidewalk and masturbate like a chimp in a zoo-cage.” ― Hunter S. Thompson, Fear and Loathing in Las Vegas