My first quilt was an Eleanor Burns QIAD Log Cabin and I did finish it in a day. But I have to tell you that the insturctor practically stood over us with a whip, in fact when a group of us went to lunch, she came and found us after half an hour and told us we needed to get backd!
Fast forward several years, and although I am not very prolific quilter, I know a lot more now than I did then. A few years ago I got to take a Trip Around the World class with Eleanor Burns. I didn't finish my top in the class, about six hours and that didn't include cutting but there was a bit of down time at the start expalining stuff before we put the pedal to the metal. Some folks did finish theirs, but I don't have the attention span to stay at it the whole time. I did have most of it done before the end of the day.