Until you've innovated your way into living and growing your food underground because the surface of the earth has become so hot or suffers from so extreme climate events that it has become impossible to actually live on it.
Until space underground becomes so scarce that it becomes impossible to live...then you innovate and terraform the atmosphere to make the surface inhabitable again.
Until space above and below ground is completely filled, and we engineer massive super-AI spaceships (i.e. The Culture series).
I see no need to stop, perhaps the heat death of the universe will put an end to things but with strange eons past even death may die.