I too have heard it said that if someone self-proclaims themselves to be in MLC, then they probably are NOT in MLC.
What if it's not a MLC, but this person decided that they have been too cautious all of their life and want to live with more adventure and less restrictions. I didn't say it has to encompass cheating.
I left the reference to Starsky's post as I believe this keeps the context.
I think that's a really good question, DLS.
I want to first take some responsibility of pointing out my own belief that MLC is a superset of a life transition. I'm sure others have stated that belief before me, I just know that I've been focusing on that a lot, especially more recently...
I would submit that if someone wants to try sky diving, we'd not be looking at that as someone taking on a more adventurous lifestyle. As you indicate though, if someone is moving from a more "safe" life to a more adventurous life... we'd probably be looking at a transition.
A transition like this may or may not "stick". The person may decide a life of adventure isn't for them and revert back to their "norm". That is still a transition as they re-discover themselves.
In the above case, a LBS would probably best just get out of the way and let the spouse figure out what they want.
How one might differentiate the above from transition to MLC, would be if a lot of the activities were either life threatening and / or extremely spontaneous. ie. Not well thought out, perhaps even irrational, as in risking monetary ruin and the well being and welfare of their nuclear family.
In the above case, the LBS would certainly want to remove themselves and any children from harms way, while still operating in a non-interfering way, in regards to the MLCer.
And again, as described by MWD in regards to a "vanilla" WAS, the WAS is not necessarily re-inventing themselves. A WAS is rather leaving a sitch which they may feel is harmful for them or otherwise no longer serving them and is not generally because they want to change who they are, as a person.
That would be one of the distinctions between a WAS and MLC / transition. The purpose appears quite different.