hotlinking - Can Someone Please help

[akko]

Ok i have a .htaccess and it works great, but eats up the CPU real bad. is there another way of doing it which will cut down the CPU load?
here is the one i have.
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://domain.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^http://www.domain.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^http://domain2.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^http://www.domain2.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^http://domain3.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^http://www.domain4.com/.*$ [NC]
RewriteRule .*\.(gif|GIF|jpg|JPG)$ - [F]

Any suggestions would be great
thxs akko