Your example seems to work really well in my brief testing that I just did and my htaccess has gone from hundreds of lines to just 30 lines.
I added a few more file types into mine.
Code:
RewriteRule .*\.(css|asf|mpg|mpeg|wmv|avi|rm|gif|jpeg|jpg|zip|png|swf|mp4|m4v)$ - [NC,F,L]