Well I think family history is a better chance at short labour.
DD1 - 41+1 - 18 hours
DD2 - 41 - 30 hours
DS - 39+5 - 5 hours.

But my mum's labours were 18, 9 & 3. All around due date.

A friend of mine has a family history of 1 - 2 hour labours on her mums side. Her first was 7.