Why does it take long time to refresh the static resource cache on the force.com site?
|Knowledge Article Number||000188006|
|Description||Salesforce uses far-future expiration dates on resources due to the use of version numbers in the path. Using a static version number or no version number at all circumvents that and results in lengthy cache expiration times for resources.|
It is highly advised to use URLFOR($Resource.ResourceName) instead of referencing /resource/ResourceName directly. Using URLFOR with the resource will put the current version number in the URL path, and that allows updates to the resource to get used instantly by the pages while maximizing the cacheability of each version.