[Castiel's expecting the explanation, the halfway-there apology, and to an extent he can even understand Dean's reasoning. In the heat of the moment Castiel had been upset that Dean would keep something so important from him, but having had over a week to think about it, he at least sees where Dean's coming from.

Of course, that doesn't necessarily mean he agrees, but there's something to be said for empathy.]

But I might be able to do something about it. I can do research here on ways to reserve it. We could make plans. It would be better than going into it blind, Dean.

[Which drags them right back to the problem with lost memories. But if Dean's going to carry on as if he'll remember all of the "good times" here, then Castiel might as well try to make the best of it on a strategic level.]