I believe other people's expectations of you greatly influence your behaviour.
Therefore it follows that if I expect my W to be honest and faithful, any actions on her part to the contrary will be incongruent with my expectations and my behaviour toward her. Her tendency would be to want to live up to my expectations.
Peter, I kinda get what you're saying, but on the other hand, everybody here expected their S to be faithful, and we all were disappointed.
I think the transparency has to be there. Whether or not you make use of that transparency every 5 minutes or every 5 weeks is where you have the latitude to show your W trust.