Do Chinese language users use 作心三日? This isn't exactly a question about the linguistic properties of the Chinese language, but something I'm just curious about.

Is 作心三日 a 成語 used in China? It's a very common Korean proverb, basically meaning that whatever someone puts their mind to, they can't last for a long period of time (literally translating to "the mindset you created, three days."

I'm just curious because I thought chengyu were pretty much the same across Chinese, Korean, and Japanese.
No, but there is a colloquial proverb (俗语) in this vein:


  三天打鱼，两天晒网
  
  sān tiān dǎ yú, liǎng tiān shài wǎng


A more modern turn of phrase is:


  五分钟热度
  
  wǔ fēnzhōng rèdù


... literally "five minutes of zeal / enthusiasm".