When do you pay the taxes if you 1031 and end up paying off the mortgage?

[Ramiro Rodriguez]

I am considering a 1031 Exchange when we decide to "move up" in home in the future. If we 1031 Exchange and end up staying in the home a paying off the mortgage are the deferred taxes due the day you pay off the property or is there a window of time in which they will be have to paid? How does that work?