12 hours might just be for the first two acts lmao (or less)
But I mean, a lot of FVNs are just HUUUGE time sinks (Shelter, Soulcreek, Tennis Ace, Killigan's Treasure, Password...) -- even the linear ones!
Which makes sense considering the often above 100k wordcount of these novels (which would, on average, take 7 hours to read through if it's just text)