ESV - 9 Know therefore that the Lord your God is God, the faithful God who keeps covenant and steadfast love with those who love him and keep his commandments, to a thousand generations.
For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
1,000 generations is between 70,000 and 80,000 years, if you go by Psalm 90:10 which says:
The days of our lives are seventy years;
And if by reason of strength they are eighty years,
Yet their boast is only labor and sorrow;
For it is soon cut off, and we fly away.