When is a change of doctrine progressive and when is it to cover up holes.
Good point. Progressive revelation, as understood by most Bible-believers is related to such things as how the Messiah, the new convenant, resurrection, etc., was revealed over time to God's people, and by divine intervention no less. It isn't quite like saying, "This is GOD'S TRUTH, accept it or die." today and then when the teaching gets too problematic (like an important date comes and goes!), saying, "UM, actually no. Pay no attention to what we said before. THIS is is God's truth now, accept it or die."