They do this when they're alone, but Valeriy "accidentally" leaves the door unlocked... maybe someone will come in and catch them. He's a professional and shouldn't do that, But when he's inside Mitya's warm mouth, he forgets his own name ...
Mitya with oral fixation, he cannot concentrate without having something in his mouth, when Valeriy wants him to shut up and concentrate, he just lets Mitya take his dick in his mouth