Well this model doesn't take one extremely important factor into account: Intelligence. Intelligence is the single most powerful force in the universe. This is a fact due to our old friend, exponentiality. While yet we still tremble before the might of an earthquake or a hurricane, in a few hundred years we will harvest the entire power of our sun and in a million years (still only 0,00000073% of the current age of the universe) we will have engaged in pastimes such as Stellar Husbandry and zero-energy computation with megascale constructions of black holes.
The death of the universe is very slow process. It will take at least 10²⁰ years for the last star to die out and 10⁸⁰ years for the (hyothetical) proton decay to become non-negligible. These are extremely long time-spans. Even if the growth of intelligence (that is us and our descendants, if we don't encounter extraterrestrial intelligence.) slows down dramatically (if, for example we can't break the barrier of the speed of light) the exponential nature of it will result in a universe saturated with intelligence, before proton decay would become a problem.
Imagine the beauty of a universe turned into a single gigantic zero-energy supercomputer running a neverending simulation (as real as everything you know and then some) of all individuals that ever were, of everything precious to intelligence. We could even create new universes from the holes in space-time occuring in the center of black holes. We truly would be gods, gods greater than every human could fathom. I deeply believe that this is the ultimate Fate of the Universe.
All hail intelligence!