Many commentators believe Gen. [[6:3|bible.1.6.3]] teaches that God's patience with mankind would last another 120 years; after this all were destroyed in the Flood. It seems unlikely to be referring to lifespans; for one thing, many people lived far longer than 120 years for centuries after the flood. "the Holy One Blessed Be He patiently warned evil mankind for one hundred and twenty years before He unleashed the Flood."
Ref-0150, p. 310.