My insomnia was brought about, I believe, by stupid shifts, in my previous job, Did a week of 7 days 6-2, then immediately swapped to 3-11, for 3 days, then 2 days off, then 3-11 for 3 days, then no break, 6-2 for 7 days. So often, if working overtime, not in bed until 2am, with a start of 6am.
Apparently that is against the law, but my bosses didn't see it like that. And apparently, having an irregualar bodyclock, means you are at more risk of a heart attack.
So there are days when I can go without sleep at all, or eating, then 24 hours in bed, followed by constant eating, and sleep in the afternoon. During winter, it was common not to see daylight, as the shifts prevented you.
Apparently pilots suffer from insomnia.