A blog is not a blog if you never update it. From my experience the best scenario is to update your blog daily and at the minimum three days a week. Blogging one day a week or just several times a month will add content to your blog but will never create the return on your time investment that regular blogging will.
I know this from personal experience. I have blogged for years on my own blog. In late 2007 and early 2008 I have some blog personnel issues, one of my blogger’s father was in a slow decline and I ended up with some very serious blog coverage issues. I needed to blog for my writer on a regular basis but typically without any advance notice. As a result, my own blog suffered. I posted infrequently or sporadically. I saw my blog readership drop from nearly 40% of my website to under 5%. I saw a huge crash in my website traffic that was very concerning.
It has taken over eight months of consistent blogging, without fail, to rebuild my blog base of regular commenter’s, blog visitor traffic, and website traffic. It was very hard work and it was slow to regain what I have built and then lost.
Blog visitors will typically not come back to revisit a blog that is half heartedly maintained. I know I don’t. So if you want to get into the blog game, make the commitment to a minimum of three days a week and stick with it. Your traffic will build and your blog and website will benefit both.