Defeat the boredom: Give players things to do. ALWAYS.

When I play Elemental or Civilization V, I like to observe how AI players evolve over the course of a game, hoping to see one or preferably two super powers emerge. That leads me to staying out of trouble unless trouble finds me. As I played Elemental in this way, I noticed it could get pretty dull while not in conflict with other players and found myself pushing the next turn button in the late game repetitively. I have a few ideas that could help that aspect of the game:

• Monsters should spawn in forests and hills, even if they lie within your influence.
• Monsters should spawn in greater numbers (spawn as armies), especially in late game to pose a threat to player armies.
• Remove adventure tech tree from the game:
  
  • Newer, more powerful creatures should be drawn automatically to cities as population increases.
  • Same for adventurers.
  • Channelers, adventurers, and offspring should be able to complete quests based on their level or the number of quests they completed (each hero has his own quest level):
    e.g. quest_level = hero_level/2
    e.g. quest_level = #_quests_completed_by_hero/5
  • All levels of quests should be available within your domain throughout the game. When one quest of a level is done, another quest of the same level spawns elsewhere. Lower level quests respawn so that offspring can level up.
  • All levels of notable locations should be visible throughout the game, and they should not respawn (questing is more enjoyable). 
  • If you really want to reveal new sources of resources, that can be moved to the civlization->harvesting part of the tech tree.