Hi Matt,
The expected default behavior is to have expire headers to be set 1 year in the future. It is weird that your expiry date is set to year 2000 (would be curious to understand why). Nevertheless, in order to control the expire date headers, you have the following options:
1) Extend WroFilter and override the WroFilter#setResponseHeaders(final HttpServletResponse response) method.
2) Extend WroFilter and override the WroFilter#newResponseHeadersConfigurer() method. This method returns ResponseHeadersConfigurer object which
3) Create another filter which is mapped to the same path as WroFilter and override the headers in doFilter method.
4) Add in wro.properties a new property with key header.
Example: header=Expires: Thu, 15 Apr 2010 20:00:00 GMT | cache-control: public
Let me know if that helps or if you have other suggestions.
Thanks,
Alex