I am going to optimize a site which has two subdomains since a long time ago. They are pointing to the site's main domain and are well-indexed by Google. I've read in a SEO book however that having several urls pointing to the same content is a bad practice bcauses waisting 'link juice'.
Now I am wondering whether removing the subdomains is a good idea SEO-wise? regarding that it causes many references from Google lead potential visitors to nowhere. It is specially helpful to know how long does it take for Google to flush references to the subdomains. I appreciate your hints about this.