I'm sorry you are stuck with this kind of person. However, having to deal with them only a few times a year is better than having to deal with them every day right? I think reminding yourself of that will help you to get through the time you spend with them. I would also suggest "yessing" them to death. No matter what they say agree they are right. Voicing your own opinions with someone like this is fruitless. Save your opinions until they are gone. I know that's not easy to do but you might try it to protect your own sanity.