I have set up W3 Total Cache to minify and combine js and css files which works brilliantly, giving me something like;
Now and again I need to change the js/css files. I had expected that when I empty my cache and the minified files are rebuilt, they'd use a new filename so that anyone revisiting the site would get versions of the js and css files.
Every time they are rebuilt, they keep using the same filename. I did think that maybe I hadn't cleared the page cache, but no matter what I do, the file name is the same.