I think its really up to you... If its relevant content and people are visiting your site and they like the content why not just keep posting to keep people coming back...
It depends on the theme of your site and blog. If u are running blog try to change content frequently and if website it is ok 6months or a year(not so frequently)..but again depends on the type of site.
obviously more frequent is better but it depends if you want to get more traffic definitely more posts are better.
blogs are supposed to be updated on a regular basis. then again, it depends on what kind of blog it is. some bloggers write on a daily basis like its their online diary. some make posts few times a year. try to make atleast 1-2 posts per week to show google that your blog is active. there is no set rule but more the better