A final report often hides the useful distinctions that produced it: which sources were strong, which assumptions were tentative, and why an alternative was rejected.
Preserve the parts that enable revision
A small record might retain the question, the original evidence, the important interpretations, the decision, and what remains unresolved. Links between them matter as much as the individual pieces.
Useful memory helps us revise our understanding when the world changes.
Test whether keeping it helps
Return to an earlier assignment with new evidence. Can you trace an important claim? Can you identify what needs updating? Does the record save more effort than it takes to maintain?
Preserving everything is not automatically useful. Retrieval, freshness, and the ability to correct earlier mistakes belong in the experiment too.