Regarding the main Ask Ubuntu site, there are two Meta questions here that I found that mention "time" and "duplicates":
Primarily: Would it be useful to allow duplicates after x time?
(To a much lesser extent): Does time get considered in deciding Duplicate Questions?. While it's more about two questions that were asked nearly simultaneously, @Oli's answer mentions:
If there is a lot of time between the questions, it may also be worth considering that they are different issues and closing the new one may not be appropriate.
But I couldn't find a Meta question where the same topic had been covered for Ask Ubuntu Meta questions.
The site has been around for nearly 12 years now, and community (and even individual) opinions can change during that time, sometimes quite a bit. Would it make sense to allow some older questions to be asked again for updated opinions and discussion without fear of them being closed as duplicates? I think we should always link back to the older discussion (either the OP or someone via edit), but it seems that it would be nice at times to have a "clean slate" discussion, even if the outcome ends up the same.