With DD (my first), I lost mucous plug about midnight, went back to bed and slept fine. I felt "odd" all morning, but figured I could not be in labor since I was not due for another 6 weeks. I noticed some leaking about 3pm, but was still deep in denial. Finally around 4pm, I figured something was up. Went to hospital at 6pm, had baby at 8:52pm. Contractions were only noticeable for the last two hours or so.
With both DSs, Water broke at 11:30 pm exactly, with contractions beginning immediately. DS1 was born at 1:56am, DS2 was born at 10:07am