Right. It's like the debate over the Textus Receptus vs. the minority text. Just because something may predate something else does not make it more truthful.
And as pointed out, there was plenty of error in those first 300-400 years floating around.
Both premil and postmil POVs existed in the early church. Just like now.
The truth, however, has not changed. The victory was won on the cross. Christ reigns today over heaven and earth. And one day at the end of time He will return in glory. We have no idea when that will be, but we are told to keep our houses in order for His return.
Life is for the living. God instructs us to be fruitful and preach His word, warning us not to foolishly look to the skies to ponder mysteries known only to God.
Christ doesn't reign over the earth-yet.
But, you are correct, we are to be about God's business, occupying until He decides to return for His Bride.