If you mean ‘forever’ literally… well, the amount of energy inside our cosmological horizon is finite, and is becoming increasingly unreachable. If you stipulate that there’s some means for humans to reach outside of our light-cone, then you have to confront with the possibility of time-travel (as far as we know). The conclusion is that ‘forever’ is either unreachable or loses its meaning once you consider sufficiently advanced tech.
If you mean ‘forever’ literally… well, the amount of energy inside our cosmological horizon is finite, and is becoming increasingly unreachable.
If you stipulate that there’s some means for humans to reach outside of our light-cone, then you have to confront with the possibility of time-travel (as far as we know).
The conclusion is that ‘forever’ is either unreachable or loses its meaning once you consider sufficiently advanced tech.