What term means being wearied or dulled due to excessive indulgence?

The term that means being wearied or dulled due to excessive indulgence is "jaded." This word captures the sense of fatigue or disillusionment that can arise when someone has experienced or consumed too much of something, leading to a loss of excitement or enthusiasm. It is often used to describe someone who has become cynical or apathetic as a result of overindulgence in pleasures or experiences.

The other choices do not convey the same meaning. "Mercurial" refers to someone who is subject to sudden changes in mood or behavior, which does not relate to the idea of being wearied from excess. "Maudlin" describes a sentimentality that is often excessive or tearful, particularly in a way that does not indicate fatigue or dullness from indulgence. "Melancholy" denotes a deep, persistent sadness or gloom, which is different from the feeling of being jaded by overindulgence. Thus, "jaded" is the most precise term for the condition described in the question.