Then we are safe. :)
What we disagree with is the presumption that God has sent a Christian the "Book of Life" to glance through so they could find their name written on it in indelible ink. That will not do. There are just too many cases in Scriptures and real life that negate that presumption.
The presumption is based on a premise of who a Christian is. Since my side has, I think, a much "tighter" definition, that would seem to take care of the cases you mention.
As long as we remain in Christ, we are guaranteed of entering the Kingdom. God is righteous and will not pull the rug out from us.
And on this we wholly agree. :)
So what is a "true" Christian? How is he identified, when WE don't know whether he will fall away in the future and our determination is proven wrong?
I personally like the biblical Catholic notion better.
Regards