I am writing a story where with an immortal race of aliens with psychic powers. Their minds are separate from their bodies and located in a pocket dimention inaccessible to ordinary matter. Their bodies are psychicly animated stone or metal. (Like Astral projection?)

Notable points:

• They can die temporarily (ie: get disconnected from their body) by being crushed or vapourised. They can re-animate their original body or construct a new body from material in a 100m radius of where they died. They can also die permanently if they run out of energy and have no way of getting more.

• They can only control one body at a time. Only one immortal can control one body at a time.

• Older immortals are more powerful than young ones. Old immortals generally control larger bodies and have more powerful psychic powers.

• They reproduce slowly (compared to humans) with a new generation every 250-500 Earth years.

• Cancer or other diseases are not an issue but they need to absorb energy or they will become less powerful and later completely impotent. Energy can be absorbed as Light and Heat. Using their psychic powers drains energy and they can absorbe energy through their stone bodies. Larger bodies require more energy but can also absorb more energy (higher surface area).

Their psychic powers include Telekinesis, Levitaion and Pyrokinesis. Moving an object telekinetically requires the same amount of energy as moving it by normal means. The same with Levitation and Pyrokinesis.

Would the Sqare-Cube law prevent them from growing past a certain point? When would population become an issue? Which of energy absorbsion or living space become an issue first? How would their civilisation form itself? What other issues might they run into from being immortal and having these psychic powers?