while Tim McGee writes a farewell letter to his late father. In Season 16 ("She"), Gibbs burnt the slip with "10: Never get personally involved in a case." Later that season ("Perennial"), he says that once he has gotten rid of a rule, the rule is gone for good. In the season 18 finale "Rule 91," he adds the titular rule to his series, stating, "When you decide to walk away, don't look back", though McGee countered in the Season 19 premiere that this was in violation of Rule 1, "never screw over a partner." Gibbs wants useful information as fast as possible and under the assumption his team has already done all the necessary legwork in advance; when this is not so, they lose face with him very quickly. Gibbs is also remarkably hostile towards idle chatter without a purpose, and things that go over his head like technobabble and medical jargon, wanting conversations to be curt and decisive. Additionally, Gibbs prefers to avoid deep conversations and will tell people if they are making him uncomfortable. He has a constant habit of sneaking up on his team members from behind and dropping in on their conversations unannounced, generally as he tells them to grab their gear before heading out to investigate a crime. It is later revealed in Season 13 that the skylight above the main office of the NCIS building reverberates when people speak and Gibbs is able to hear echoes of what they say coming into the room and eavesdrop. Gibbs is a habitual coffee drinker. When his coffee is spilled or someone else takes and/or drinks it without knowing (this also translates to stolen food that is his), it almost always causes his temper to flare, and he will demand a new one; at least once, however, he has done so simply to haze somebody, in particular McGee when he was a new team member. He even considers coffee the equivalent of breakfast, as seen when he was offered a selection of food from a diner, Abby asked him to at least have something before he left, and Gibbs merely grabbed the coffee cup. Up until the middle of season 13, Gibbs has more or less abandoned the upstairs bedroom of his house in favor of sleeping on the couch downstairs, since he has no inclination to keep his domestic habits attractive living by himself, especially