[Plugin: WP Super Cache] Expired Files Not Being Deleted

My expired files are not being deleted. Prior to using WP Super Cache I was using WP-Cache which was working well. I’m using an expire time of three hours (10800 seconds) and I’ve set Garbage Collection to run after 1000 requests. The site this is running on gets about 25,000 page views per day, so I’d expect Garbage Collection would run about once per hour.

So far I’ve never seen any evidence Garbage Collection has run. I’ve been monitoring the number of expired files reported over the past couple of days and it just keeps climbing. Once I get a few thousand expired files I figure it is time to manually hit the ‘Delete expired’ button which will– after a few tries, clear out all of the expired files and start at zero again.

Where does the counter for Requests before Garbage Collection exist so I can try to troubleshoot what is going on? Is the Requests counter based on any page view? Any page view served from wp-cached files? Any page view served from super-cached files?