I reckon the length of my (spontaneous) labours have (so far) been rather perfect - for me.
With both boys I birthed for approx 7-8 hours, of which only probably the final 90 mins was "hard yakka". The first 5-6 hours was a gradual build up of contractions and intensity, making both my births "perfectly manageable".

Honestly though, I don't think "perfect" is a one-size-fits-all scenario