IMO it all depends what you want to get out of the PR? Links? Saturation? Positive Impressions? Create Buzz?
If you’re just rolling the dice for links, you’re hitting 1-10 at best, so you might as well run it all though a Markov generator and dump it all over the place as comment spam, you’ll have just as much luck.
If you’re looking for saturation, I suggest doing one or two a week and have them translated, you will save time on writing, and still get a high number of important brand reference points with a much more diverse audience.
If you are looking for Positive Impressions, I would suggest trying to lay one earth shattering PR a week and nail it hard in Social Media and News (i.e. Digg, Reddit, Boing Boing, Stumble Upon.
If you want to keep a buzz, you need to blow it up daily with articles, tagged re-hashed images from social, free flash games, videos, jokes, quotes, whatever it takes to get the hits.
So I guess all I’m saying is, it’s not about How often as much as it is about, Who, What, Why, Where, When, and why care. :notify: