No I do not believe OSAS....There are just to many warnings in God's word about turning our backs on Him and what will happen if we do. If the teaching OSAS was biblical God would not have needed to warn us.
(John 15:6 NIV) If anyone does not remain in me, he is like a branch that is thrown away and withers; such branches are picked up, thrown into the fire and burned.
(Hebrews 10:26-27 NIV) [26] If we deliberately keep on sinning after we have received the knowledge of the truth, no sacrifice for sins is left, [27] but only a fearful expectation of judgment and of raging fire that will consume the enemies of God.
You can't claim salvation through faith in Jesus Christ and live like the world. If you do then you are part of the world and have no part in Christ. I am not saying that a Christian will never stumble and fall into sin, but their life will not be characterized by sin, or they are not a Christian.
(James 4:4 NIV) You adulterous people, don't you know that friendship with the world is hatred toward God? Anyone who chooses to be a friend of the world becomes an enemy of God.
Look very closely at this passage from James. First it shows choice; "anyone who chooses..." Then it says "becomes an enemy of God." Those two statements are vitally important. Sinners (non-believers) do not choose to be friends with the world, they are the world. Next, sinners (non-believers) do not become enemies of God, they were born enemies of God, just like all us of were. So what is James saying? He is saying that if you are a Christian yet you choose to be friends with the world, meaning to indulge in the sins of the world and live as the world, then you become an enemy of God. He is referring to people who choose to follow the world instead of following Christ. Don't let people fool you about this, you can't walk away from Christ and still retain your position in heaven.