People like me may have ideas to add to old discussions. I'm scared to revive "dead threads" from 2014, etc.
How long until a thread is considered dead?
https://subeta.net/help/rules.php?act=rule&id=36
The rule about posting on old threads. Most are no posting on threads older than 3 months, except for the specific ones listed on the page. Although I believe the rule was altered recently to include a 15 month rule for those forums.
If you have something to add to a thread older than that, you should just make a new thread for the topic.
Only S&I was changed to 15 months afaik. Site feedback and P&B are still unlimited, while all other forums are 3 months.