As an analogy think about how we feel about people 2000 years ago - if we could have just a few comprehensive samples of something in their world, we would really like it. Even things like exhaustive lists of every word they said for a week would be incredibly useful for linguists, lists of everything they ate would be useful, etc.
We shouldn't rely on their choices of what is worth preserving - we should adopt a broad based approach and try to preserve the maximum amount of things, and hope it will be useful later on.
I think today we have even used graffiti preserved on the walls of Pompei to get an idea of what the ancient world was like - surely there would be valuable information stored in even an imperfectly-frozen brain?
Who knows what kind of crazy theories they may have in the future, that they just would need to have a few brains to test out with?