Flog something to death
Definition 1 of 1
Pro Tip 1/3Overuse Warning
Use the phrase sparingly to avoid sounding repetitive or boring your audience. 
After the fifth meeting about efficiency, he began to flog the topic to death.
Pro Tip 2/3Negative Tone
This phrase often implies frustration or annoyance with how much a subject is repeated. 
She flogged her argument to death, and we were all irritated by the end.
Pro Tip 3/3Conversation Shift
Suggest changing the subject if someone is flogging a point to death, to keep conversations fresh. 
Can we talk about something new? You've flogged that rumor to death.