I think there is a real problem with many confusing God’s infinite mercy and grace. It’s only infinite because it comes from an infinite God. But one day it will cease. R.C. Sproul makes the point well:
When God judges people according to the standard of his righteousness, he is declaring that he will not strive with mankind forever. We hear all the time about God’s infinite grace and mercy. I cringe when I hear it. God’s mercy in infinite insofar as it is mercy bestowed upon us by a Being who is infinite, but when the term infinite is used to describe his mercy rather than his person, I have problems with it because the Bible makes very clear that there is a limit to God’s mercy. There is a limit to his grace, and he is determined not to pour out his mercy on impenitent people forever. There is a time, as the Old Testament repeatedly reports, particularly in the book of the prophet Jeremiah, that God stops being gracious with people, and he gives them over to their sin.
From Romans: St. Andrews Expositional Commentary.