Well I guess they can be some what shorter. My first was 25 hours (I seem to labour long) and not very nice (long story and I don't want to scare anyone).

My second was 18 hours but pushed bubs out on my own so it was a much nicer experience as far as that goes. It's just tiring having to labour so long.

I'm hoping to get my 3rd down to 12 hours.