Suppose an old closed question has an historical lock on it, making impossible to vote/comment/flag on any post.

What should we do if such questions have a high visibility but contains *some* outdated or wrong information? https://meta.stackexchange.com/questions/156219/what-if-the-answers-of-a-historical-locked-question-become-obsolete#156226 indicates that such questions should be unlocked (and potentially removed), but what about cases where *most* of the information is still accurate and useful?

For instance:

https://stackoverflow.com/questions/155964/what-are-best-practices-that-you-use-when-writing-objective-c-and-cocoa

I think this post still deserves a historical lock as the information provided is indeed useful. Only little parts of it are gradually becoming outdated and still being hit every time one queries for *cocoa best practices*.

What should we do when a historical-locked question provides, say 85% of useful up-to-date information and 15% of outdated one?