I feel the answer is NEVER. You must describe the content of the article, not the length. Some journals publish notes separately from regular papers, and often even encourage their submission by offering speedy refereeing and publication (even the Annals encourages "short", i.e. under 20 pp. papers). Anyhow, if your paper is published as a note it will have "Note" written on it anyway, so no need to be redundant.

More generally, you should emphasize not the length but the content. If you prove that all tennis balls are white make the title "All tennis balls are white". If you prove that some tennis balls are white, title your note "On white tennis balls", or "New examples of white tennis balls" or whatever. If your note is a new simple proof, and this is what you want to emphasize, make the title "Short proof that all tennis balls are white". If there was a conjecture that all tennis balls were white and you found a counterexample, use "Not all tennis balls are white". If you study further color properties of white tennis balls, use "A remark on white tennis balls". You see the idea.

On the other hand, if you wrote a survey, it important to emphasize that, regardless whether it's long or short. That's because this is a property of the content and style of presentation. For example, "A survey on white tennis balls" or "White tennis balls, a survey in colored pictures", etc. In fact, if your title is "A short survey on tennis balls colors", that would mean that your survey is short in content, as in "brief, incomplete", rather than in length - an important info for the reader to know.