Speaking at a BAFTA Q&A for BioShock Infinite attended by Digital Spy, the creative director said it then took just two drafts to write because of that lengthy "painful" discussion process.
"[Ideas are] like waking up and finding that the elves had made the toys, quite often," he explained.
"It's usually because you've gone through a very, very painful process of lots of frustrating discussions.
"You fail, and you walk out of those discussions and then you work on it for weeks and weeks, and then you're in the shower all of a sudden, you go, 'Oh God, of course'.
"It comes out of nowhere. But it's not like it's easy; it's because you've done all that work of breaking it down before. Very rarely we get a great idea right out of the blue.
"The ending of this game took us four months of talking, and then I wrote it in two drafts. Because of the talking was where we did the breaking it down, it was very quick."
Levine added that the ideas process is often "a lot of complex things trying to be made into a few very simple things", and that things don't always work out.
"Sometimes the ideas never come, sometimes you get stuck with shipping stuff you're not crazy about," he explained. "But you know, pencils down."