Hi all,
We've just had a big chat about this with the techs and developers and looked into everyone's settings and we can see you're all set to see all the posts. Just so you know, threads older than 30 days aren't excluded from Active unless users explicitly want them to be. The option is there but most don't take it up.
What that means is that your thread, and the other long-running threads, are subject to the same conditions as any other thread on the site, conditions that fwiw pre-date the introduction of 'similar threads'.
Clearly, however, it's not feeling that way to everyone. That may be a function of the site being bigger, there being more competition for 'Active' altogether. You want your threads to be seen, and used, and available - fair enough on a discussion site, of all places.
What we can suggest is for you to flag to everyone on your favourite long-running threads that they should use 'Save' to see updates to saved threads, and when that results in more usage, it will also result in more "Active", iyswwm? And so on.
We'd like to reassure you that the more technically-minded MNHQers are most definitely aware of your concerns, and if that anything occurs to them that might assist further you'll be the first to know. We understand the value of the long-running threads to the feel of MN, and we're more than aware of and grateful for your contribution. Some of us are even old enough to remember Lissie's Pub (because some of us are ancient...) and know how important these open, welcoming threads are to new members.
So yes, you've given us a lot to think about, actually, thanks for raising it. 