Indeed, Hickey does get what she's talking about. He finds it hard to keep his hunger sated on a good day. Here? When they're dealing with all this? He's battling that hunger pretty much every day. It's threatening to take him over and make all his decisions.

"How long d'you think something like this will last? You'd think the darkness would have to break eventually."

There's an unspoken 'but...' after his sentence. You'd think the darkness would have to break but it hasn't so far.