I'm running a Django app w/ Nginx and Apache. All our static media is stored on S3, and basically it takes a while for the app to check if thumbnails have been created every time a page is loaded. To alleviate this problem, I'm caching the output of the templates w/ memcached. Over the course of an hour or two, the site's speed goes down significantly, until I restart apache, and then all is good for a little while.

I have very little sysadmin experience, and was hoping somebody could at least point me in the right direction.