Do you know anything about black holes or dwarf stars? Like roughly how long they last? Also you seem to think heat death is for sure and it's not. Not at all. It's the current most popular theory but crunch and rip are still fully possible.

Silly scifi goth

Based on what we know right now, I agree. There is more about physics that we don't understand than what we do, and who knows what might be harnessed!

Humans won't be doing any of the harnessing, of course. That species is fucked.