What if the unfaithful partner doesn't and hasn't contributed anything toward purchasing any of the accumulated possessions, investments or savings. Let me clarify here that I am not talking about SAHM's here, I am talking about those who for whatever reason choose not to work and bring in income and then cheat to boot.
(Zeroth: In the case you describe the WS doesn't sound like a good future risk; maybe a divorce is better here than a post-nup?)
First, you have to be fair in the assessment. As you suggested, household chores count in the same way that dollars earned do.
For a complete slacker, I'm a lot less tolerant here. I'd have to think the length of the M is important. Was the WS always a slacker in a longish M? Then the BS seems to have accepted it, so nothing seems a little hard. In a short M I would think there wouldn't be so many assets, so its not a significant issue. If WS worked hard in the M for many years and just for a few goofed off, you have to be fair in the accounting.
Every situation is different. What if the Betrayed Spouse is cruel and unkind for many years in the marriage. The WS cheats; signs a post-nup; and cheats.
Is what the WS did right or okay. Of course not! They are accountable. But why are we trying to apportion financial assets only for betrayal, and not potentially other aspects of the relationship (addictions, abuse, cruelty, neglect)?
None of us had/have perfect marriages. Any of our faults, no matter how slight we may believe they are, hurt our spouses. Is infidelity uniquely painful -- I think so. But its not the whole story.
My $0.04.
- WG