Say, let's suppose the universe ends in an open universe, with the Universe expanding, but not going to such an extent that the big rip theory will take place. Obviously, the only things left would be stellar remnants and perhaps debris such as asteroids or comets in deep freeze.
Then suppose that many civilizations have teamed together to survive this end, and they have complicated technology, such as, but not limited to faster than light travel, star or planet manipulation, and the ability to create artificial black holes, artificial wormholes(assuming they exist), and many other things if they have the energy and resources to do so.
The distance between galaxies are super large at this point, probably several trillion parsecs. Now, suppose that this time is where white dwarfs have all burned out, and neutron stars have either died due to neutron decay(assuming this is possible), or swallowed by black holes. Now, we see that that the universe is made of loose rocks and debris with black holes scattered around trillions of parsecs.
Then, suppose a groups of living beings want to live on in such a universe. There are no other energy generation methods that will last, and last forever(ex. solar, wind, water, nuclear, putting asteroids in black holes and collecting the energy...). Thus, they use a simple energy/heat generation method, tidal forces. They make a binary planet system with the two planets close enough and rotating/orbiting around the barycenter fast enough with each other to generate heat via tidal forces. The tidal forces' generated heat power should power wind and water power via convection.
Now, we know that binary systems are not forever. They eventually spiral together. We can suppose that the living beings have thousands of engines that will activate and propel the planets away from each other so their previous orbit if the orbit spirals too in, powered by the heat energy from the tidal forces on each planet to avoid such thing from happening.
This model should be a feasible counter for such end of the universe. Now, is this model viable, or is there some kind of flaw in my thinking that will render such model null?
If you need clarification, just ask and I will elaborate.