You don't put version info at the end of your filename, you just append a "version" query parameter when you reference the CSS resources.
- Don't change CSS/JS (or other static file) filenames, just change contents
- Refer to those files in your HTML via
<link rel="stylesheet" type="text/css" href="//host/path/file.css?version">
- Everytime you change contents you increase version. You could also use application versions, but you'd have to make sure they do not repeat.
- Default caching on static files is 10min. You can set your own cache expiration.