I don't see a problem with leaving it for overnight. I think I've done that before & don't remember it being an issue. The next time I pin baste I'm going to try it by leaving the pins open. I can't remember if I read that on this board or on a blog somewhere but it sounded good to me. I also read that one quilter left her pins in while she did stippling & just stippled around her pins. That way she didn't have to take them out during the quilting process & it saved a lot of time. These are a couple of things I want to try in the future.