Upside, I've often wondered what would have happened if my H hadn't seen a C. Certainly, he was making some progress without one. He didn't tell me a lot of what he discussed with the C, but he did say, "I should have done this years ago!" The counselling seemed to resolve a lot of issues for him. Even though the C told my H, "I don't believe there is such a thing as a MLC," he did diagnose him as being depressed, work on his childhood issues like physical abuse from his mother, help him do grief work for his mother and others who had died, teach him to engage his mature brain, explain how the relationship with the OW was a fantasy (and gave him a deadline to decide between us), teach him how to handle withdrawal from OW as if from any other addictive substance, and get him to take a family-first stance at work. I'm sure it would have taken a LOT longer for him to get through all these issues without professional help, because he'd never been given the tools he needed before.
I considered myself to have been bombed on the day of H's Awakening, when I finally got him to admit he'd been staying in another town regularly not for work but to spend time with OW, and that he was glad I finally knew about it, and that it wasn't really a "friendship" he had for her.
However, his actual bombing (the closest he came to ILYBNILWY was the day he 4 months later told me that "something was missing" and maybe he should move out. He claimed that since he'd met OW, he didn't have feelings for me, and was sure he wouldn't get them back because the day he met me he stopped caring about his highschool girlfriend, and broke up with her and never cared for her again.
The odd thing was, he'd broken up with his former girlfriend a good 2 to 3 years before I met him and was quite ready for another relationship. Because I could see how confused he was in his thinking about that, the actual bombing seemed likely to me to involve a certain amount of confusion as well.
This bomb was somewhere in his Depression stage, about 3 1/2 months before he decided to work on the marriage. These were also the months of intense C for him. As Wonka said, the timing of the bomb can vary a lot owing to personal circumstances.