Basically, you should post whenever you have something interesting to tell your readers, and post often enough that they don't lose interest. I'm quite willing to wait a while for one of Dover Canyon's stories (although I love the excitement of Tom Wark's daily posts).
I'd rather have a good post once a week, than a mediocre post every day. (Hint: if you like taking digital pictures, taking an interesting one and writing a little bit about it is an easy way to create good posts). That's why I suggested 30-60 minutes to put one together. A good post takes a little time (for me, anyway).
As I said in my original post, posting more often tends to be better (assuming there's good content in those posts), but I also know that most wineries don't have dedicated bloggers, and most of their potential readers don't use an RSS reader to read blogs by subscription (yet) - instead they read by visiting the blog itself. So, once a week is a reasonable minimum. If it becomes a chore for a winery blogger (owner, winemaker, marketing director, tasting room manager, ...) to think up something to post, their blog is doomed.
These aren't wine bloggers, these are *winery* bloggers! Many small winery owners (who stand to benefit the most from blogs) just want to make wine, which is why you see poorly-thought-through Web sites and no winery blogs. A winery blog is a way of involving readers in the story of your wines. Tell the story well, and those readers will buy your wine, and pass the story along to others (and maybe they'll buy, too). In your reader's minds, blogging sets your winery apart from all those who apparently don't have anything interesting to say about their wines.
I'm trying for a reasonable compromise here. After all, I want to encourage wineries to dip their toes in the water and tell us their stories. Hopefully, some of them will catch the bug. Right now, exactly none of the winery blogs on our list are posting regularly each week.
Personally, I'm ready to help any winery that wants to blog with advice and encouragement (and a subscription to their RSS feed). And I know Lenn is, too (particularly those Long Island wineries).