I've played 54 in the past on an unlimited golf package at Boyne in Northern MI. It's really not that tough, especially if you're not travelling much between courses. You do however need to do two things. First you obviously need to get an early start. Second, you need to catch the courses when they aren't terribly busy. You aren't going to get in 54 holes with 5+ hour rounds (frankly why would you even want to if that were the case...).
That was all when I was in my 20s and early 30s. These days, my preference is to just play 18-36 holes and find something else enjoyable/relaxing to do the rest of the time.