>is it ever too late for a man to redeem himself?
Yes, from the moment Adam ate of the fruit.
>Is it ever too late for God to redeem man?
No, because with God all things are possible, but tbh tons of people give no indication of being redeemable.
I think what you're really wondering is at what point does one become a reprobate. Only God knows.
Definition of reprobation:
God's eternal resolve to exclude certain rational creatures from eternal happiness. As taught by the Church, God has eternally predestined certain persons, on account of their sins, to rejection from heaven. Always understood is that God wants all human beings to be saved, but he does not wish to save those who, by their abuse of divine grace, freely separate themselves from his love. (Etym. Latin reprobare, to reject, condemn.)