For performance reasons we recently configured the server (using site rules) to add far-future expires headers to those resources. That way, the resources are cached on the user's workstation and served from the cache until the expiry date. The browser doesn't even check on the server if the resource is different from the local version. This gave us quite an increase in performance (a lot less HTTP GET's to be performed an every request).
WebBooster however, seems to overwrite the expires header with a date/time that is approximately 1 hour before the time that the image was served to the browser.
Any thoughts on this? Is this by design? Can it be disabled for certain paths?