That said, I'm sympathetic to creators; I've written several (unpublished) novels myself.
Most novels don't support the authors that write them. There's no argument to be made that Jane Doe's 20,000th-ranked novel makes her nothing in the third year instead of three dollars.
At the other end of the scale you have George R.R. Martin. I'm sure he would be fine with or without the revenue from HBO's GoT. That said, in that particular case I think it's likely that HBO would want his blessing in any case -- especially since he hadn't written the ending yet. Without his cooperation, would people have been as likely to watch knowing the ending was made up by someone else?
So then you have the mid-tier authors -- a misnomer since really you're talking about the 99.9th percentile, where GRRM is the 99.9999th. But in any case, I still think that the vast majority of the revenue from a novel generally comes in the first 2-3 years. If losing that last, let's say 5%, makes the difference between success and starvation, that seems like a rare case to me -- even for authors who write slowly.
As for retirement, I'm not sure how to answer except to say let's pick an author who is clearly self-supporting, but not GRRM: Piers Anthony. He's still cranking out Xanth novels (last I checked). Do you suppose sales from his Battle Circle books (published in the '60s and '70s) are contributing materially to his retirement? Ha, I just checked and he's up to 45 books in the Xanth series. :-)