Thanks, Speed, for posting the question of how rock bottom may manifest itself. I've learned quite a bit from reading the answers provided so far.
I've been pondering the following question:
It sounds to me that an MLCer after hitting rock bottom assumes personal responsibility for the damage they caused and hopefully is a wiser man/woman for the remaining journey in their life. What if this doesn't happen, i.e. they don't assume personal responsibility and make poor choices? Have they not hit rock bottom yet and got stuck in the tunnel? Or, are these personality traits or disorders that were not affected by MLC/rock bottom?
One of my BILs just got married for the second time and seems to set himself and his new wife up for unhappiness. He (now 53) married a woman about 15 years younger than him - she wants a child while he does not. In his first marriage, he left his wife and children, claiming that his children's busy after-school schedule made him an alcoholic. He took a job in another state and moved away (similarly to H, who moved abroad a year ago for a job). He probably hit rock bottom (or several rock bottoms) with his former addiction but I'm not sure how this affected his MLC.
Not assuming personal responsibility and having young partners is also FIL's way of life: After his 1st marriage of 20 years ended (MIL packed a suitcase one day and left, leaving the four children aged about 11-19 behind; lots of cheating on both sides before, possibly both were going through MLC), FIL remarried (one of his OW?). ExW2 was 17 years younger, that marriage lasted seven years (reason why it broke apart: "She was too lenient with her kids, giving them sweets before dinner."; new reason that H heard for the first time last month from FIL: "She cheated."). H told me that FIL was very depressed after his second marriage collapsed (rock bottom?). W3 is about 23 years younger than him and that marriage is not based on love, but on convenience (which, I guess, works for some people).