It's a perennial problem -- even posters who have been on the forums for a long time continue to make it: not noticing that a thread is old (even ancient).

My suggestion is to make old threads age visually. Maybe the edges could appear with a graphic making them look like old paper (yellowed or weathered . . . )

Or, if that's too tricky, then the date could be in an extra large font or a different, bright color when a thread's last post is over six months old.

I like the idea very well. I've noticed the same thing happening before.

Maybe make a topic a closed topic automatically after so many months with no posts in it. It could always be reopened by a moderator if needed.

I guess one might change the font to "old English". But seriously- I never understood what would be wrong with reviving an old thread.

I like the idea but maybe not change the entire thread but make older posts in that thread look older?

I think that this should work gradually, so 2 year old posts should look older than 1 year old posts. So just 1 font would not work.