It should be mentioned that all (or at least most) ideas to survive the heat death of the universe involve speculative physics. Moreover, you have to deal with infinities. If everyone is suffering but there is one sentient being that experiences a happy moment every million years, does this mean that there is an infinite amount of suffering and an infite amount of happiness and the future is of neutral value? If any future with an infinite amount of suffering is bad, does this mean that it is good if sentient life does not exists forever? There is no obvious answer to these questions.
It should be mentioned that all (or at least most) ideas to survive the heat death of the universe involve speculative physics. Moreover, you have to deal with infinities. If everyone is suffering but there is one sentient being that experiences a happy moment every million years, does this mean that there is an infinite amount of suffering and an infite amount of happiness and the future is of neutral value? If any future with an infinite amount of suffering is bad, does this mean that it is good if sentient life does not exists forever? There is no obvious answer to these questions.