With my first unsuccessful vbac I pushed for about 2.5 hours, but I had been induced by AROM and DD was asynclictic. I ended up with another cesarean. I completely regret that whole hospital vbac experience. Their limit for pushing was 2 hours for a vbac mother. A whole 3 hours or so for a non-vbac mother.
My second vbac, an hba2c at my midwife's house, my water broke at 11:30 pm, I had about 30 minutes of totally intense contractions, then started pushing in the car and pushed for about 1.5 hours total, partly in the car, partly at my midwife's house in the tub. It was an awesome experience!