If we get into a state of sin of any type, be it adultry or blasphemy or whatever, and never repented, we are lost.
1 John 5:14-17 addresses sin unto death - The best short summary of this passage I have found is this:
"the sin unto death is that which results in the total apostasy of the sinner, leading to a state which is hopeless, not because of any limitation on God's part, but because of the will of the sinner not to accept pardon. "
I think we are in agreement.
...b