If you look closely, this note appears only on topics that have a (more or less) clear question and a solution (most times marked as [Solved]).
If the question is solved, I set it to autoclose after 168h (7d), in order to keep the topics in useful shape.
Or in other words: People tend to unearth old threads. They have the very same problem as described in the topic, only the device is different and he is using 17.01.4 instead of 17.01.0-rc2 as in the original topic, and by the way, his setup is completely different and his solution is completely different to the original topic.
When topics are closed you have: one topic, one question, one solution. Period.
Topics stay short, instead of accumulating new postings, going into hundreds which nobody reads, drifting offtopic, adding unwanted noise, ...
In case someone feels like a topic should be reopened: No problem, can be done anytime.
In general, I ask if the topic has been solved for the OP, suggesting him to mark the topic as [Solved], and after he has done that, I set the topic to autoclose.
Asking the OP is a learning from earlier this year, when a regular user (who is is no longer a user of this forum upon his own request) set a topic which wasn't his own one to solved, but turned out that it wasn't really solved.
Why autoclose instead of immediate close?
Maybe sometime after the [Solved] shows up, the OP has new information, e.g. the solution worked for 24h, but not at 24+1. Or some sideeffects of the solution show up only 2days after the solution... we all know such situations.
This topic will close 6 days after the last reply
This means, if someone makes a new post at now+5d, the countdown is reset and you will still have 6 days left again. And so on, until no new postings arrive in this topic for 6 days.
I think I have seen a plugin for discourse that allows the user to do the [Solved] marking in a more elegant way, i.e. by a simple button click. In addition to this, he can mark the posting which solved his problem, giving the "solver" credits for the solution. I'll search for this plugin again, maybe it could be useful.
...browser history is your friend: https://meta.discourse.org/t/discourse-solved-accepted-answer-plugin/30155
@jow @thess What do you think of this plugin, worth a try?