The 3 minute checkpoint is only helpful if you shut down fah many times a week. Otherwise the fraction of a second the client takes to write a check point 480 times a day actually slows down your client a very small amount. But this adds up over time. And what you save on shutdowns is more than lost by writing so many checkpoints.
Recommending 3 minute checkpoints for everyone may not be the best policy. It depends on how often you stop and start fah. On dedicated machines that run 24/7, I recommend the max setting of 30 minutes. On most systems I don't recommend anything lower than 5 minutes.
It also depends on the work units you are running. If your frame times are every 7 minutes, the client saves a check point at those completed frames, and you don't really need one every 3 minutes.
The 15 minute default was set there for a good reason. It's a good compromise between how much time is lost in a shut down versus how much time is lost by writing extra checkpoints hundreds of times a day.
Use your best judgement in how you fold. Don't accept recommendations blindly.