I noticed that new rules earlier this week when I tried to report some old posts from our local board. I didn't realise it was a general rule; I thought it was exclusively for my local board.
So now this risk is mitigated. However, I believe that the 6 months is a very short life span for a post to be eligible to be reported. Maybe allowing reports from 2-3 years back would be more useful. For a long time now mods are not overwhelmed by the number of reports, therefore limiting the reports to only 6 months seems too short...
I'd say 6 months is great. Is there any reason to report an old post when we have a ton of current spam reports still unhandled? Old posts will only be moderated if they fail to meet the criteria mentioned on the report page, an old topic without a single or few spam replies is likely to get moderated .