With my 2nd I planned on waiting til the contractions were only 5 minutes apart, even though I was a 40 minute drive from the hospital.
I ended up having contractions on & off for 20 hours though. Then when they became regular they were 30 minutes apart, but they were unbearable, so I woke DH up to go.
As soon as I did they hit 5 minutes apart. I got to the hospital at about 3am, 7cm dialated & she was born at 7.08am. So we were still there for 4 hours.