I remember watching a movie in which a fighter pilot was constantly showing off by "buzzing" the control tower. Time after time, the pilot is warned he'd be grounded if he didn't stop. I'm guessing the person who wrote the story thought the pilot was cool and such an "Ace" the commanding officer would never do anything to cause him to lose his best pilot. In the real world, the pilot would not only be grounded, he'd receive a dishonorable discharge for his repeated failure to obey a direct order.
     Some readers won't catch the mistakes. If your novel is about what happens in an emergency room, anyone without medical training might not know the difference between forceps and retractors. A surgeon or nurse will, or at least should, notice the mistake. If they're like me, even the little mistakes I catch drive me crazy.
     I'm not saying there's nothing in my novels that will cause people in law enforcement to shake their heads or send me emails telling me about the mistakes. All I'm saying is you have to do your research. Technology, clothing, and behaviors need to be appropriate for the historical setting of the novel. Characters and locations need to be appropriate for the geographical setting of the novel. And, unless a character is prejudice against a group of people, never rely on the common misconceptions and stereotypes of that group.
     Coming up with the idea for a story and the actual writing can often take much less time than any research needed to make the novel historically, geographically, and technologically correct. Even if you work in the medical or law enforcement fields, research might still be required if you introduce activities outside of your specific sphere of expertise. In order to make your characters and plot believable, take as long as is needed to have the correct facts. Do your research.
     Why do you have to be accurate and factual if you're writing a novel? My book is a good example to use. The primary audience will be any Christians who want a story with Christian themes. Even though some people will disagree with some of the doctrine mentioned, it won't have to do with misquoted facts, it will be a difference of theological opinion. However, a secondary audience will be people in law enforcement who just happen to enjoy reading about crime and the police. I better have my facts straight if I don't want any of those people telling their friends not to read it because it's nowhere close to being correct. And if I want a positive review from someone within law enforcement to use as a blurb on my cover, I want them to realize I at least attempted to stay true to police procedure.
     My advice is that if you don't want to spend the time doing the research, stick to writing about something you know every detail about. This will make your task of writing easier and save you embarrassment later.