Tenured Radical had a great post the other day called "Senior Scholars, This is Your Conscience Speaking" in which she tells us to get moving on those book manuscripts we're supposed to review. She's absolutely right, but I'd like to add one small demurral.
Deadlines are deadlines for a reason, and we ought to honor them. This goes double for tenure review deadlines, which are usually due late in the summer. I've never been late and am usually early with these, because someone's career is on the line.
The same mostly holds true with reviewing book and article manuscript submissions. But (and you knew there was a "but" coming) deadlines for reviewing manuscripts are not pieces of flair. Remember in Office Space where the manager tells Jennifer Aniston's character that wearing 15 pieces of flair is the minimum, but if she really were serious about her job and not a slacker, she'd want to wear more? If an editor says "We would appreciate receiving your review by August 30," I assume that this is a real deadline and that this isn't a hint that I should want to get it in sooner and will be considered a slacker if I don't. Of course everyone wants to get things done early, but that doesn't always happen. If I only have 15 pieces of flair here and get the thing in by the stated deadline, I'm still doing all right.
To get back to Tenured Radical's example: I think it's up to the editor. If the editor from the press wants it by the middle of the summer so that the author can do corrections in late July and August, he or she will tell me so and set a deadline in June or July--and, in fact, those have been more customary deadlines for book manuscript reviews than late August.
So do what Tenured Radical says and get those manuscripts reviewed and out the door. But just because they're resting on your "to-do" pile doesn't mean that they have to be in your guilt pile, too.