To Cache or Not To Cache

I'm building an app that has to traverse huge arrays slices to get aggregate data.
I could cache the results, but it's unlikely that the same slice will be selected again. I'm wondering if it's worth the memory.
I'm caching the per-all aggregate data, which I read only once anyway.

Caching is not applicable where it would save time, yet applicable where it doesn't matter.

Cute, eh?