Let's say you are saved. If you are sinning at the exact moment of your death (anger, having bad thoughts, etc)---say a car or truck crashes into your car and you die instantly---will you go to hell? If you were lusting over someone the night before, and you know you'll probably do it again, and you die, will you go to hell?
The question you pose really asks whether or not every sin constitutes an act of apostasy, to which the answer is clearly not, but some sin can be of itself a wanton act of apostacy:
2Ti 2:11-13
Here is a trustworthy saying: If we died with him, we will also live with him; if we endure, we will also reign with him. If we disown him, he will also disown us;
if we are faithless, he remains faithful, for he cannot disown himself.
There is the sin that leads to death, and the sin that does not lead to death.
1 John 5:16
If you see any brother or sister commit a sin that does not lead to death, you should pray and God will give them life. I refer to those whose sin does not lead to death. There is a sin that leads to death. I am not saying that you should pray about that.
However the "sin that leads to death" may be more venial for an older believer, than for a new believer, because as Christ pointed out, the more you know, or claim to know, the more guilt is attributable to your sins.
John 9:41
Jesus said, “If you were blind, you would not be guilty of sin; but now that you claim you can see, your guilt remains."
The thing is, are we conscionably despising the LORD's word and breaking his commands? That is the question, but if we are doing it at all, whether just before death or any time, we are on very dicey grounds spiritually.