To be honest – still confused. I am totally unable to replicate this behaviour and looking again at the DB query that populates the data – and the code that arranges it – there is nothing in there to stop old topics being listed. The only real item that should or might effect it is permission settings. It it is all fairly straightforward.
As an aside I have also tried to load up Quick Cache (not Pro of course) but am unable to test with that active and/or disabled because it just doesn’t work for me! Followed all the instructions and I don’t think I am daft, but it just fail’s to cache anything!