I quite like the Plank as an exercise. Most people can do them and it doesn’t require any equipment. However, I don’t really see the point in doing them for 3, 4 or even 5 minutes at a time. I’m not sure you will be accomplishing much. Especially when compared to thinking about what you are doing (i.e. training smarter) to get the most out of the exercise in a shorter period of time.
Additionally, once this basic Plank is done well, you can progress onto all sorts of variations.
Here’s a short video of how to get the most out of doing the Plank.