Google Webmaster Sitemap how often welcome back to index ?

Hi to all good evening,

Iwas looking in my webmaster tool google sitemap and i saw Last Downloaded 1 hour ago so

More i put content uniquw one every day does it help mimes messages in my newsgroup to be seen ?

Is it better to work in a group and only work with sitemap submitting or use rss submitter same time please ?

thanks a lot
:cow_yello