When is a Rebuild Over?

This is a question that I've been thinking about a decent amount the past month or so: When is a rebuild over? 

Is it when a team has a winning record? Makes the postseason? Wins the division? Wins a series in the postseason? Makes it to a certain round? Wins a championship?

Just curious what everyone thinks, because not every rebuild ends in a title, so how do you measure when one phase is over and a new one has begun?