It's very true; despite their history and the antics they get up to, as couple they're actually pretty boring. Which is totally fine by them - their lives are dramatic enough, they need a place that's kind of quiet and boring. They're perfectly happy to have that with each other.

"Awww, why not? If anyone can convince them, it's you." He's grinning as he says that, but it's still true. Annabeth certainly is the most convincing person he knows.