With DD I left home when contractions were 2 mins apart, the hospital was a half hour drive & being my first bub I didnt want to be having her on the side of the rd so I didnt wait at home any longer.
When I got to the hospital they were going to send me home until they did the internal & I was 4cm dilated so they kept me in. DD didnt arrive for anther 11 hours though.

With DS I had my waters broken in hospital to get labour started which it did & 4 & half hours later I was holding DS.

I think most people (especially with their first?) would leave home when contractions are around 2 mins apart, I could be wrong though!

Good luck for when the time comes