I see these articles about all the matter in the universe dying one day and it all seems too speculative to me. Extrapolation beyond any reasonable timescale is guessing. Sure particles can die but new matter is being created too. If matter is leaving our universe through black holes then it must be entering our universe from black holes in other universes. Some of those universes would be younger than ours so the matter would be longer lived than the original matter in our universe. So the universe is being constantly replenished with fresh matter. Also who is to say another universe or two might not pop up inside our universe in the next few trillion years? It could alreadsy be happening. That would explain why the part of the universe we inhabit seems to be expanding at an increasingly rapid rate. So maybe the universe will last forever.