Never! I have never left behind a forums old threads through 15 years and five different forum/CMS tools (OpenACS, Joomla plus a bridged in forum, Drupal 6, Drupal 7, and now Discourse).
And, I don’t want to add more categories. It’s just too much for casual users. New users already post in the wrong category about half the time. Sometimes I think to move it to the right one.
You’re right! That is so not intuitive. I’ve looked for that feature a bunch of times…but, since it exists, I’ll give a try to not auto-closing topics so quickly. Thanks for pointing this out! I’ve even googled this question a couple of times, and tied poking around a bunch and never stumbled on the right incantations to make it happen. This was one of the big things bugging me about Discourse (which is already much better than we have any right to expect free software to be).