In today's world, audiences turn to radio for specific programming. There are too many choices to risk deviating from the format that your audience is used to. If your station is a news station, news is what your audience expects. Unless you are planning a complete format change and are aiming to capture a new audience, do not deviate from this format. You'll lost your audience for sure! If your station is country formatted, if you start adding anything other than country, you'll probably lose your audience!
Minor format modifications are necessary and usually safe to implement but don't go too far. Here's an example, my station Edgewater Gold Radio has been playing solid oldies for 17 years. About a year ago, I added a very short history segment which aired about three times during the day. The segment was about 2 minutes long. I monitored the audience closely while the segment was airing and I was very surprised to see that the audience dropped off during this time. I make a decision and removed the segment.
In my experience, consistency is key. You can't fool your audience and if you want to retain listeners---------stay the course!!