htaccess: poner fecha de expiración a las imágenes, css, js

<ifmodule mod_expires.c>
 ExpiresActive On
 ExpiresDefault A3600
 <filesmatch ".(jpg|JPG|gif|GIF|png|css|ico|js)$">
  ExpiresDefault "Expira en 7"
 </filesmatch>
</ifmodule>
También se puede poner así:
<ifmodule mod_expires.c>
    ExpiresActive On
  ExpiresDefault "access plus 1 seconds"
  ExpiresByType text/html "access plus 1 seconds"
  ExpiresByType image/x-icon "access plus 2592000 seconds"
  ExpiresByType image/gif "access plus 2592000 seconds"
  ExpiresByType image/jpeg "access plus 2592000 seconds"
  ExpiresByType image/png "access plus 2592000 seconds"
  ExpiresByType text/css "access plus 604800 seconds"
  ExpiresByType text/javascript "access plus 86400 seconds"
  ExpiresByType application/x-javascript "access plus 86400 seconds"
    </ifmodule>
Para que te haga caso las indicaciones anteriores:
# Cache One year for image files
<filesMatch ".(jpg|jpeg|png|gif|ico|swf)$">
Header set Cache-Control "max-age=31536000, public"
</filesMatch>
# Cache One month for css and js
<filesMatch ".(css|js)$">
Header set Cache-Control "max-age=2628000, public"
</filesMatch>


En el caso de los tipos de letras (woff y demás) hay que hacer antes arribe del todo:
AddType application/vnd.ms-fontobject .eot 
AddType application/x-font-ttf .ttf
AddType application/x-font-opentype .otf
AddType application/x-font-woff .woff
AddType image/svg+xml .svg

Y luego en el <ifmodule mod_expires.c poner:
...
ExpiresByType application/vnd.ms-fontobject "access plus 1 month"
ExpiresByType application/x-font-ttf "access plus 1 month"
ExpiresByType application/x-font-opentype "access plus 1 month"
ExpiresByType application/x-font-woff "access plus 1 month"
ExpiresByType image/svg+xml "access plus 1 month"

 O si quieres distintos tiempos según el tipo de archivo :
<ifmodule mod_expires.c>
 ExpiresActive On
 ExpiresDefault A3600
 <FilesMatch ".(gif|jpg|jpeg|png|ico|swf)$">
 # 2 semanas
 ExpiresDefault A604800
 Header append Cache-Control "public"
 </FilesMatch>
 <FilesMatch ".(xml|txt|html)$">
 # 2 h
 ExpiresDefault A604800
 Header append Cache-Control "public"
 </FilesMatch>
 <FilesMatch ".(js|css)$">
 # 3 dias
 ExpiresDefault A604800
 Header append Cache-Control "public"
 </FilesMatch>
</ifmodule>