The "144,000 barrier" is anothr consideration. Apostasy or no apostasy, JW's cannot afford to allow the existence of "true Christians" as an organized body much beyond the first century.
That is a good point TD. As I was typing the response the 144,000 issue flashed through my mind. It's probably one of the main reasons that Watchtower insists apostasy took over Christianity immediately after the 1st Century. Can't have too many years go by, or it won't add up to a total of 144,000 being reached in the 20th Century; it would have been reached much sooner. Actually, the math on the 144,000 is a big problem anyway.