Historicism is whack. The day to year principle in Revelation just doesn't work. Imagine giving Christ 1000 years and the beast 1260 years.
Not to mention, as I have quoted before, these guys read a verse about the people who have the mark of the beast having sores on them and interpret it as the french revolution. What a joke.
With that type of interpretation I may as well say it was the plague in Europe that cut the population in half, would be a much better fit atleast, but still unbiblical and out of touch, as all the other vials have to be poured out within that 42 month period as well.