Lessons. There's no such thing as learnings.
If you're fine with the generalized form "learned a lesson", then surely "learnings" is fine too. There's no point in trying to police a completely normal and sensible use of language.
Anyway, I accept this usage of the word "lesson", so I also accept "learnings". My point was one of hypocrisy, not policing people in how they can use the word "lesson".