A New Solution To The Fermi Paradox

A paper in the Journal of the British Interplanetary Society puts forward a new hypothesis for the Fermi paradox.

Their hypothesis in a nutshell: Aliens are asleep, waiting for the universe to cool down  so they can do more computations with less energy wasted cooling their computers.

Not very convincing in my opinion. If expected return on each unit of energy spent computing is positive now, why wait until later?