It probably varied from area to area. A friend having a baby in north London in 1967 was discharged from hospital after 6 hours. We were all shocked.
In 1971 in Berkshire, I was kept in for a week after the birth, less than 2 years later, for DD, I, too was discharged officially after 6 hours, but as that would have meant a 7.00am discharge, I wasn't discharged until nearly lunch time.
DH has always had a 'thing' about car safety and fitted front seat belts in his car in about 1966/67, and insisted people used them. With babies we had a carrycot harness in the back of the car and, even for the trip home from hospital, the baby was in the carry cot and strapped in.
Six months later his insistence on car safety saved us from serious injury, if not death, in a car accident. It was the weekend after he had fitted the britax child safety seat in the back for DS. We were all wearing our seat belts and were driving along a country road when someone pulled out from a side road. DH managed to avoid hitting him, but we went across a verge and into a hedge, decelerating heavily. If we had n't been wearing seat belts we would have been catapulted through the wind screen and if DS had been on my lap...........