[The moment Percy calls him "shorty" is the moment Nico deems the question and all previous statements as unworthy of comment. He takes another piece of dark chocolate and eats that before answering his second question.]

You say that like he doesn't do that any other day. To answer your question, though, no, not really. It gets a bit busier this time of year because it's a little easier for spirits to find themselves in the mortal world. Or escape. Granted, that's not counting the spirits bound to the mortal plane anyway.