"So .. maybe rock bottom isn't like a sudden flash of lightning ...but a period of time??"
I think so, Sophie. My H began hitting bottom in January 2007. It was an intense period of late-night "breakdowns" on the phone. It was off and on for over a month, then he retreated again.
He hit again a few times over the next several months, though less intensely, but retreated each time. In my H's case, it was a series of hits and now he seems to be much more like his old self. He's not that selfish, irresponsible, immature person anymore .. at least not like he was, lol!