If you're a member of a committee, no matter at what level, do your shit on time.
What happens to you if you don't? Well, nothing. And you still get to put on your CV that you served because, really, who's going to check? Especially if you're tenured and stuff.
But if you don't do said shit on time, or you do a quarter-assed job of it, and if said work has hard deadlines, then you know what happens?
Answer: The chair of the freaking committee does all the work you didn't. Yea, even if it means that she's up in the office until 7 p.m. on a Friday, two hours after declining invites from friendly colleagues for end-of-week, post-faculty-research-seminar drinks and socializing, because she's making sure everything gets done.
Or so I've heard.