This word was used by the Stoics and the Pythagoreans. It is in the papyri also. We must put no fantastic ideas into the mouth of Jesus. But he did look for the final consummation of his kingdom. What is meant by the disciples also sitting on twelve thrones is not clear.
Eternal life is the real reward.
This paradoxical enigma is probably in the nature of a rebuke to Peter and refers to ranks in the kingdom. There are many other possible applications. The following parable illustrates it.