I'm "Bard" rank right now.I know, i lose AG points if i don't keep playing regularly. I just wondered that:
When i complete all of the quests i will reach to "King" rank. But what should a King do to keep his/her rank? Only way is merits?
Your rank is based on a % of the total amount of points you can get from quests, points from merits are a bouns. If new quests were added you may lose a rank, to get it back you have to earn some points from quests or merits.
Also take a look at this pleasde: https://support.armorgames.com/hc/en-us/articles/231778768