Hi Donncha, FolioVision,
I am pretty sure there is a bug or a misconceived issue here. And I will try to explain myself better:
1) I have 'preload' turned on for all posts. I do NOT have preload on for categories, tags, etc.
2) I have garbage collection set to run every hour (3600 seconds) with timeout for files set to 600 seconds. It DOES state "next garbage collection <time>" on that page. However, it also states:
"Warning! PRELOAD MODE activated. Supercache files will not be deleted regardless of age."
3) So category or tag pages have now been older than one week - and I see absolutely no method or way to make them refresh for visitors. It is a major issue for us.
So the way I see it, despite NOT having preload set for categories and other taxonomies, garbage collection actually does nothing because preload is turned on for everything else. And, also, there is just never ever a method by which pages are refreshed. Despite having "Cache rebuild. Serve a supercache file to anonymous users while a new file is being generated" checked - it just never does anything to refresh these pages.
The only pages that are fresh are posts, which get rebuilt when they are published or updated; and pages (such as the homepage) where I manually added prune_super_cache() to their update function...
I should point out all this began since the latest upgrade, a couple of weeks ago.
Thanks,
Bira