adding ExpiresDefault to .htaccess file

Question

I have updated my .htaccess file to include the following:

<FilesMatch "\.(css|js)$">
ExpiresDefault "access plus 1 month"
</FilesMatch>

I am trying to tell the client that all css and js wont change for 1 month so they can cache they files.

I have 2 questions,

1. Is this going to achieve what I want

2. Since adding that I am now getting a 500 error, the whole .htaccess file is below:

   
   <FilesMatch "*\.(css|js)$">
   ExpiresDefault "access plus 1 month"
   </FilesMatch>
   # BEGIN Compression (DEFLATE)
   <IfModule mod_deflate.c>
   # Enable compression
   AddOutputFilterByType DEFLATE text/css text/javascript application/x-javascript text/html ``text/plain text/xml image/x-icon
   <IfModule mod_setenvif.c>
   BrowserMatch ^Mozilla/4 gzip-only-text/html
   BrowserMatch ^Mozilla/4\.0[678] no-gzip
   BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
   BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html
   </IfModule>
   <IfModule mod_headers.c>
   # Make sure proxies deliver correct content
   Header append Vary User-Agent env=!dont-vary
   # Ensure proxies deliver compressed content correctly
   Header append Vary Accept-Encoding
   </IfModule>
   </IfModule>
   # END Compression (DEFLATE)

Answer 1

Make sure ExpiresActive ON is set inside of your FilesMatch directive before ExpiresDefault.