In a closed system, any process that occurs will tend to increase the total entropy of the system as time passes.
— Second Law of Thermodynamics
It's not just that all things must come to an end, but that the longer that series, books, and games go on, and the more changes they undergo, the likelier it is that something will get lost as time goes by. For example:
- Adaptation Decay: The act of adapting one work into another distorts it. In an extreme case, the original work is not even recognizable in the adaptation.
- Badass Decay: A character who comes across as badass at first isn't portrayed like that anymore later on.
- Magazine Decay: Later issues of a magazine don't maintain the theme it started with.
- Menace Decay: The behavior of a child character — even that of a nominal menace — gets less vexatious over time.
- Motive Decay: A character's goal gets less and less central to their portrayal.
- Network Decay: Later programming on a TV network doesn't maintain the theme it started with.
- Seasonal Rot (aka Season Decay): An entry in a series has notably lower quality then the other entries in the series people are used to.
- Trailer Joke Decay: A joke isn't as funny in a movie if you see it in the trailers over and over.
- Trope Decay: A trope ends up getting used differently from how it's originally defined.
- Uniqueness Decay: Something gets treated as rare early on, only to progressively be shown as more common.
- Villain Decay: A villain gets less and less scary as the series goes on.
