Use the term kingdom come to mean "forever" or "heaven." You might sigh that you'll be cleaning up the sand your brother's dog tracked around your apartment until kingdom come.
Saying you'll do something until kingdom come is an exaggerated way to express your feeling that it will last forever — until the end of time. An alternate way to use the expression is to mean "the next world," which implies an afterlife, or death. An action movie bad guy might threaten to use a bomb to "blow you all to kingdom come." The origin is Biblical; it's thought to come from the line from the Lord's Prayer, "thy kingdom come."