Greed for enlightenment and immortality is no different than greed for material wealth. It is self-centered and dualistic, and thus an obstacle to true attainment. Therefore these states are never achieved by those who covet them; rather, they are the reward of the virtuous.
For unflagging interest and enjoyment, a household of children, if things go reasonably well, certainly all other forms of success and achievement lose their importance by comparison.