Could someone please tell me if labour is quicker the 2nd time- i know it usually is in humans!

Not been my experience with dogs.

My Kizi had 9 pups in under 3 hours first time.  3 years later it took 12 hours.

My vet told us before our girl whelped her second litter, that she would take longer 2nd time round, she said the bitch would 'pace' herself, sleep longer and more deeply between pups and she was right!

My bitches second litter took longer, but she didnt sleep between pups, just rested.

I'd say depending on how long the gap is and how many pups she's having

Both litters were the same size (9) - first time three and a half hours, second time just over 12 hours. Pups in second litter all weighed around the same - in the first most weighed a good deal more.