Research for a piece can continue indefinitely when every answer opens another tab. A stopping rule helps you identify what the draft actually needs before curiosity becomes a way of postponing the writing.
Start with one claim or scene detail that requires checking. Write the minimum evidence needed to use it responsibly: perhaps a primary document, a definition with scope, or confirmation of a date. Keep optional background questions on a separate list.
Decide what happens if the answer stays missing
You might remove the claim, narrow it, or state the uncertainty. Do not invent a plausible detail merely because the allocated research time has ended. A deadline limits the investigation; it does not create evidence.
For an invented example, an essay needs to identify when a building opened. Finding photographs of the street may be interesting but does not answer that question. If the available sources only establish a range, the sentence should preserve that range.
Save the source, the relevant location within it and the date you checked it. Those notes make later fact-checking faster than a bookmark with no explanation of why it mattered.
When the required questions are answered or explicitly removed from scope, return to the draft. You can continue exploring later, but the piece should not quietly acquire unsupported details just to justify the time already spent researching them.
Editorial illustration from this site’s image library; not documentary evidence of the example or object discussed.