Free Grace, here's a Catch 22 for you, 2 in fact. According to you, those who do what 2 Pet 1:5-11 (my signature) below exhorts will not just go to Heaven, but receive an Abundant Entrance, or more Rewards. Well, very good then. I'm going to aim for that, and work for that, by God's Grace. When a mere earthly job or whatever promises more rewards, how many people rush to try to have it. So much more should we store Treasures in Heaven, as the Lord said, by doing Good Works.
And where I disagree is not indeed that those who don't labor more won't be rewarded more; they will, be as also 1 Cor 3:8, and 3:13-15 says, but that these Good Works, by God's Grace, "help confirm our calling and election". If you need to do something to confirm a plane ticket, say, it's not confirmed already. That's why this verse is strong evidence against OSAS.
OSAS is true if we mean Once Justified, Always Justified. Once Baptized, Always Baptized. Once Sanctified, Always Sanctified. And also, if you Persevere in Faith, or in Good Works, then you received the Grace to Persevere from the Lord.
But not once saved, always saved, in the sense you mean it. I agree if you sin little, and don't work for the Lord, you'll lose rewards from Him. Such persons will be "saved, but only through fire", with their works burned up as 1 Cor 3:13-14 also says. But if you sin gravely, unto death, and don't repent at all, and even turn your back on Christ, you won't be saved at all.
But, here's the 2nd Catch 22 for you. According to you, most everyone who has ever said a 30 Second Sinners Prayers (and I'm sure most on this forum have said it, including me; and including most non-OSASers) are once saved, always saved, and nothing absolutely whatever they do or don't do can change then. Well, very good then, we're pretty much all saved then!
Final question: if someone who you believe was OSAS has now backslidden from Christ and is an Atheist, would you even try to Evangelize him? According to you, he's still going to Heaven, right? If you sin gravely, i.e. unto death, you lose Christ, or the Holy Spirit, Who is our life. If you die without having Christ in you, you cannot go to Heaven. That's why it says clearly:
"6God “will repay each one according to his deeds.” 7To those who by perseverance in doing good seek glory, honor, and immortality, He will give eternal life. (Rom 2:6-7) King David (Psa 62:2) and King Solomon (Prov 24:12) said similar things.
Notice that Jesus Christ Himself says the same as Rom 2:6 in Rev 22:12, which means it still applies in the New Covenant:
"12“Behold, I am coming soon, and My reward is with Me, to give to each one according to what he has done." (Rev 22:12)
God Bless.