"I've always wondered about that. Is it just how... your body operates, Jim?"

She knows enough about coffee now, knows the addictive function of it, but it's not to say that Holden doesn't sleep because he doesn't want to. She's had enough insomniatic nights herself to understand the eluding nature of sleep without cause or logic. Perhaps his body is only accustomed to small amounts of sleep.

Or perhaps something else keeps him up.

"What you've become comfortable with?"