The reason you have "all of this time" is because you will know a long while before things get really ugly (to the point of an RO) that the marriage is in trouble. I realize that once an RO is put in place it's already to late to sell, or hide anything. No one goes from a blissful relationship one day, and then suddenly wakes up "surprised" with an RO the next day. I suppose it
could happen in the rare case of a cheating spouse that's a good enough actress that you never even suspected a problem, but this would be the exception, and the op already said his friend realizes that there is trouble brewing like happens in most situations.
WRT to lesson 1. No one ever knows how they (or their spouse will act/react in a divorce as things can get ugly very easily depending on circumstances. Lesson 2. I have to say I agree with all the way, but alas, most of us lose focus and fall into it at some point anyway.