Open one realm at level 70 instead of two realms at level 75. Give players at high levels more items challenges and high ticket items.
By level 70, the last item for purchase is unlocked and challenges are likely long since completed. the only incentive to continue playing is to unlock two realms at level 75. However, it takes so long to level up at this point in the game, there's nothing to inspire the effort. Besides, at level 75 there's nothing new to buy - what do we need two empty realms for at that point -- not to mention the final two that are still unavailable at this time. Why not change one of these realms to open at level 70, when space is at a premium. Also introduce new challenges and items that are at a higher level.