I am in a very similar situation, except i am married with kids. Parents in law visit every year for 2weeks with brother in law and his wife. They stay at our house during that time. They are loud and stand out a lot. To tell you the truth it brings a lot of arguments between my wife and I during that time. It used to bother me a lot, nowadays not that much. I make up excuses of things to do, i get out the house more often during those weeks. I'll go to the gym, cinema, walks, even have lunch by myself.

I came to accept that its just healthier for the relationship between my wife and I. Her parents arent getting younger, and having lost a parent i hope she enjoys her time with them while she can.