There is no doubt that honesty is important in a relationship. A relationship that is not based on 100% honesty is the one that experiences infidelity and eventually a divorce. This is equally important when a couple realizes that both men and women are polyamorous and it is perfectly normal for people to wish that they want to make love to a person that they are not married to or are not in a monogamous relationship with.
A couple that has figured this out is Will Smith and Jada Pinkett. He says in an interview that if he likes another girl, he shares his thoughts with his wife. So all those women who have a fit because their husband even look at another woman need to get a life. It is impossible not to look at attractive people.
Will Smith says that he and his wife will share it with each other if they sleep with someone else. He makes another good point that it is better if a spouse finds out about it before it happens or soon after and from his/her spouse rather than from someone else. I think he did not mean swinging but that is not for everyone anyway.