[ D's not wrong, but the reminder doesn't go very far in assuaging his concerns (of which they are many). Though there is a little blip of embarrassment at the nice sentiment of his return that clouds the air between them before he brushes it away.

He won't be so easily distracted!! ]

And what happens when we're not here? You saw what he was like after the Oracle. [ When he died. ] We can't always be there to take care of him.

[ That's just the way life goes. He's already disappeared once, and then died after that. He's not fool enough to think that he's filled some sort of quota rendering him immune to dissipating or disappearing yet again, and he's not fool enough to believe that Gray and D will forever be around even if he isn't. ]