Post History
Subplots are generally thematically related to the main plot. They provide thematic elaboration or counterpoint to the theme of the main plot. If your subplots are doing that for you main plot, the...
Answer
#4: Attribution notice removed
Source: https://writers.stackexchange.com/a/27857 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/27857 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
Subplots are generally thematically related to the main plot. They provide thematic elaboration or counterpoint to the theme of the main plot. If your subplots are doing that for you main plot, then they are enriching the reader's experience and they should stay. If they are just more business, then they should go. (Whether that is to another work of not is a different question entirely.)