There are actually a lot of unchecked premises behind the idea that the universe is expanding, especially since non-Big Bang theorists can find other explanations for the so-called effects of the post Big Bang era. But if one could show that it was the internal energy of the universe that was leading to the expansion, then in a sense the energy of the universe could be used up or so defused that there would not be energetic areas within the universe (no hot spots). But no one has been able to show that and according to the latest theories that even claim that, it would be something like 10 trillion years before the universe expanded so much that “everything would stop”. So, if you think they can predict out 10 trillion years, then have at it.
The point is that even for entropy, one must be losing energy somewhere for the machinery to slow down and to stop, or the energy must become so dispersed that there is no longer any place for high energy to move to low energy areas. And like I said, maybe after 10 trillion years, so I’m not going to take them at their word for that one.
One reason I am not going to take their word at that is the fact that given our current advanced knowledge about how the solar system began and how it behaves using the latest mathematical models, they can’t even predict other solar systems, which are turning out to be very strange according to our models. I’m not faulting scientists for this lack of knowledge, considering they have only had one solar system to study over the past 300 years, but it just goes to show that it’s reality first, not mathematical models first.