Persona 4 golden was 74 hours. Some people some a lot more time than they need in battles and dungeons. I didn't sprint towards through the dungeons either.
It took me 90 hours to beat Persona 4 Golden, 80 to beat Persona 3 FES. But I lent P3P and P4G to a friend and he beat both them around 50 hours. Not sure if Persona 5 will be the same, but you can probably rush it on the easier difficulties.