"He who is often rebuked and stiffens his neck will be destroyed suddenly, with no remedy" (29:1). Does it mean it can be too late?

The saying names a man by two things: he "is often rebuked", and he "stiffens his neck" (29:1) (tap stiffens). It says what comes to him: he "will be destroyed suddenly, with no remedy" (29:1) (tap remedy). In Hebrew its last four words are the last four words of a saying about "A worthless person, a man of iniquity" (Proverbs 6:12): "He will be broken suddenly, and that without remedy" (Proverbs 6:15). 29:1 doesn't say how many rebukes, or when suddenly comes, and these notes don't either. The book holds other sayings beside it. Wisdom calls, "Turn at my reproof" (Proverbs 1:23), and a saying of the chapter before says, "He who conceals his sins doesn’t prosper, but whoever confesses and renounces them finds mercy" (Proverbs 28:13). The notes on Proverbs 1 ask a question like this one of "Then they will call on me, but I will not answer" (Proverbs 1:28). 29:1 names no one, and these notes apply it to no one.