Abstract: Abstract: What does the finiteness of the de Sitter entropy teach us about cosmology? In this talk, I will present evidence that it puts a bound on the amount of (quasi-)exponential expansion that can be sustained in semi-classical gravity. We will see how this bound arises by considering a new quantum state of de Sitter space - the Unruh-de Sitter state - which is the cosmological analogue of the Unruh state that describes evaporating black holes. I will compare and contrast the obtained bound with other recent works that suggest that quantum (gravity) effects limit the lifetime of de Sitter space.