I am reaching real hard into past science classes so if I am completely wrong please let me know.
But from my understanding Space is not really empty, its filled to a real low degree with the basic elements, for example hydrogen. I am assuming that there is a finite amount of matter in the universe, so as the universe expands the "Pressure" of hydrogen through out the universe should go down, if we get to a point where there is not enough hydrogen to fill all available space do we get pockets of space that have 0 physical matter inside of them and if this occurs what happens in this area?
I remember reading somewhere about matter being created and destroyed instantly in areas where there is 0 matter, doing a quick google this is known as zero point energy. If the universe is spreading apart creating pockets where there is 0 local matter, then I am conceiving of points where matter is created from the zero state fluctuation of the universe, it seems "usually" this matter self annihilates, but would this self annihilation impart some energy into the system. So if the universe is spreading fast enough, it could be powering that spread using this energy, which then produces more and on and on and on. 1 case out of near infinity some matter could survive its annihilation just like during the big bang and thus more matter is created, so along an "infinite timeline", "infinite energy" and "infinite matter" could be created.
Gathering from the local conversation it looks like galaxy physics hold onto their forms due to the "strong" forces, so individual galaxies may suffer heat death, but the overall heat death would not occur due to the slow inclusion of new matter from these points. Overall that means that the few endings of the universe that I learned growing up could be non starters (heat death, big crunch, etc...).
… So I apologize I did not mean to throw that word vomit at you. But if someone wants to pick this apart and correct the weird model I am forming I would appreciate it.