I think you're wildly overestimating the amount of time he's away from home; he cut back on appearances a couple years ago, specifically because they took up too much writing time. He does promotional stuff for the show when each season starts, and goes to a few conventions (some of them local) every year, but that's not "huge chunks"... unless you're a pessimist.
And if he were really worried about the show ruining his ending, he wouldn't still be giving the producers details about what's to come so they can undermine him further. All you have to do is look at the writing-related posts on his blog to get that this is not someone in search of motivation to work. He's slow, he took on too many other projects after finishing Dance
, and he easily loses control of project length. That's the story.