On a fresh install the setting for “Clean cache after” is 40 minutes. For some websites this is too little. But when setting it to 120 min. (or higher) the number does not fit in the field. Could you please expand the field?
Maybe a dropdown setting the number to minutes, days or weeks could be helpful here – not all sites are updated or added with new contents regularly. So this would help to keep the cached version for small sites with few visitors, too.
Keep on the great work!