Just a tip for those of us with a large number of pages.
I had my site set up with a page warming script that kept my 4000 pages cached. It was a CRON job that ran every 4 hours.
I noticed though that sometimes, despite all that, some pages were slow to load and this DROVE ME CRAZY.
Garbage collection time was the issue.
Make sure you set it to a long enough time that you shouldnt have to worry about pages being deleted.
It may be simple to some of you but it has made the difference to my site.
I love this plugin!
God bless Frederick!