As it is very difficult to get Apache tomcat allow caching of static files (js, css, image files) on client browsers, I reconfigured my Varnish to set cache expiry time for a month or so. This actually works well. After loading all files once (when OPAC is accessed first time), the newer browsers do not query the webserver for all those static files, which means a huge decrease of load on the webserver. Here is an amazing write up on how caching works:
http://betterexplained.com/articles/how-to-optimize-your-site-with-http-caching/If any one is using Varnish I can post my varnish conf file here.