Question For Free Gracers

See the discusion here http://free-grace.blogspot.com/2007/12/so-youre-born-again-but-will-you-walk_19.html

Let us say there was a person who, since the very moment he came to believe Jesus' promises for eternal life, lived a life in total obedience to The Father. His meat was to do his Father's will, and he was always about his Father's business. This was so for many years.

One day though he fell into temptation and lay with a woman not his wife, and died during this adulteress affair.

1) would this disqualify him from being considered an overcomer?

2) Wouldn't that mean that one cannot know for sure that they are an overcomer until they are on their deathbed, just minutes away from death?