this post by Chris Brogan definitely enlightened me.
Now when I wrote my blog, telling the world how close I'm to starting up, simply I do follow the mantra "blog something, when you've got something worth to say".
This may sound silly, but I think that giving high value pills from your life, you can have more interested readers than posting something just to keep your blog alive.
Of course, it is a "consecutio" that since you product is alive and you spend a lot of time improving it, you've got a lot of interesting stuff to post :-)
My take on it is that three posts a week is great as long as you have the time, and enough valuable content to provide. Don't post three times a week just because you were told to. Figure out what makes sense for you and your readers. I would recommend asking your readers this question, and getting their take on it. They're the ones you have to please.
If it were me, I would spread out the three posts through out the week, instead of posting all three at once. For example one on Monday, one on Wednesday and one on Friday.
There isn't a right choice, and I think whatever you choose will be fine. The most important thing is to be consistent. So whether you go with three posts in one day or three posts spread out through out the week, stick with it. That way your readers will know what to expect.
Just write a blog post whenever you feel like it, whenever you think you have something to say or share. Do not worry too much about rules and schedules... unless you have a lot of stuff to write about and it makes sense to divide it into multiple blog posts per week.
I read a lot of blogs, many have set schedules so you know when a new post will be available, however, I usually enjoy more the ones that come up unexpectedly in my RSS reader, if a blog is worth reading it, readers will wait for new posts, regardless of the schedule or consistency.
Remember that people are different and have different opinions, I am sure that whatever schedule (or lack of) you end up choosing, some people will love it and others will hate it, that is just the way it is :)
If this is a business blog, and you have a large list/backlog of information to share with customers, it makes sense. Also, you may be able to break up a topic into smaller pieces.
I can't imagine a large number of readers in any industry willing to read a blog because it comes out 3 times a week instead of two especially if it is well researched and thought out-it's worth the wait.
You can't probably produce valuable posts more then 1 time a week, unless you spend all you time writing posts.