Well once the Alienest reaches a certain level(dont have the books with me) thye gain eternal youth, however it says they are stolen away by beings from the Far Realms when their time is up. I thought this would make an excellent plot hook, your playes could try to save the Alienest. A Far Realms adventure would be very fun to run i imagine. Although whether the Alienest would want to leave the Far Realms is another matter entirely.