Hi, First off thank you so much for the great plugin and all of your continued effort and support.

We average 100k users / 1 million page views /day. We find that the load on our site fluctuates depending on the time of the day. This leaves us to either modify the expire time manually throughout the day to keep to an ideal level or to set the number based on our peak to avoid getting to many cached files built up. The latter obviously results in us having a very small number of posts cached during low load times.

If the ideal situation is to keep the number of files below ~500, would it be possible to have a self tuning expire time based on the number of files found during last GC? If the value is > 500 adjust expire down, if it is < 500 adjust up.