For the first sentence, do you intend to use past tense? Because "once too often" implies either past or future tense. I don't know if I've ever seen it used in present tense. That doesn't mean it's wrong, necessarily, so if anyone thinks otherwise, please let me know. If you mean to use past tense, I recommend using "watched" instead of "watches". If you mean future tense, "will watch" may be better. As for the second sentence, it's grammatically correct and makes complete sense. Although, the typical phrase used for heating hands or other body parts is to "warm" the hands, not to "heat" them. Saying "to heat his hands" makes sense, but "to warm his hands" sounds more natural. The third sentence sounds great! It seems natural, makes sense, and looks wonderful overall. I hope I didn't confuse you at all.