Well, when I first started in 1971, 6-8 hours was common, put a sandwich in your pocket and go, and a ‘short’ formal day was 4 hours.
I think the last 8 hour day I had was with Red Rock. In the early 90s, Loudoun/ Loudoun West met at 1 pm on Sundays and I recall coming back to the meet after dark a few times.
I do remember very reluctantly pulling out in the middle of a helluva day after 4+ hours at Warrenton behind the late Michael Power, since I had to beat the school bus home, fetch kid, go teach a class at church. I cut it so close that I simply taught the class in my hunting togs, with the horse hanging out munching hay in the trailer in the church parking lot. I was not excommunicated and the kids got a kick out of it.
Sadly, diminishing hunt country does limit a lot of hunts to a couple of hours to four hours max these days. Which, for me, does have a bearing on whether I schlepp my kit somewhere, go through the expense of hiring a horse and capping, for just a couple of hours. Car following is the less expensive option there.