Maybe that's an act too. Maybe she doesn't get tired. Lucius allows himself this small, petty, suspicious observation before he dismisses it. In a past life, he used to be rather good at negotiation, knowing when to apply pressure and when to leave it for another day, assuming that that's a luxury either of them will afford the other. Presumably, Vanessza has quite a few to spare, at least.

"Perhaps I ought leave you to your thoughts," he says, partially over a shoulder as he wanders away a little to concede some space. His tone, for once, is not overly transparent, and doesn't signify code for his own desire to leave... but assuming that this meeting is fit to continue much longer seems assumptive.