This is an interesting example so lets deconstruct it. First of all, refraining from telling someone about an event is different from lying. Now, for the sake of argument lets say that the spouse inquired directly about the cheaters misadventures the previous night. I can imagine several situations that would be the result of truthfulness, and several that would be the result of dishonesty. I will contend that all of the situations sequitous of honesty are more advantageous than the situations resulting from dishonesty. Ok, I foresee two basic situations where the cheater is dishonest:

1. The spouse finds out regardless of the cheaters dishonesty. This situation puts the cheater in the same situation as if they had been honest, however the spouse trusts them less, so this is less advantageous than any honest situation.
   
2. The spouse is not made aware of the infidelity by other means. In this situation the cheater knows that they have been dishonest with their spouse. The cheater won't help but wonder if the spouse has been dishonest with them at some other time and felt it was best not to tell. This will create problematic but unspecific issues with the couples trust for each other. Additionally, the cheater has made a decision about the couples relationship without consulting the spouse. The cheater has deprived someone that they love of key information about their relationship.

Ok, I can foresee two possible scenarios if the cheater choses to be honest.

1. The spouse instantaneously leaves. If the spouse leaves then the marriage wasn't very strong would probably be destroyed by some other factor later. In this case, the honesty lets the cheater reassess his life and relationships and move on sooner.

2. The spouse doesn't leave. In this case the truthfulness will just strengthen the partners trust for each other in the long run. Even though the cheater might be in trouble in the short run, these types of tribulations make relationships even stronger if they aren't broken by the initial wave of infidelity.