The default display range for that subforum was 100 days, so when a thread is older than 100 days old, it would no longer be displayed by default.

We changed it to one year, now.

Forums have these display limits in order to reduce the load on our database. We are such a large community, they are necessary.

However, you can change your own thread display age cut-off preference in your Options:

https://psychcentralforums.com/profi...do=editoptions

Look for the section called "Thread Display Options" and change the Default Thread Age Cut Off from "Use Forum Default" to "Show All Threads."