I'm wondering if anyone knows where the line is drawn between "too short" and "long enough".
Me too. I've always had nicely developed meta descriptions, although I know I'm getting clobbered with dup filters being an ecom site where it's very difficult in this case to have completely different content/meta tags on each and every page.
So I've started shortening the static part of the meta description to help the variable part of the description be more of a factor in the complete description.
But, how short is too short? In a few cases the variable is only two words (but can be several more) and the static part is maybe 5 words. If I leave the static part as it's been (a couple of sentences), then it takes up about 80-90% of the complete description, and we're back to dup content.