I've had a Zojirushi boiler for about 6 years and have only descaled it twice. It's very easy, you just dump some citric acid in there, set it to the cleaning cycle, and dump the water out. Rinse it a couple times to remove any extra citric acid, though that's only for flavor reasons; it's food-grade citric acid.

The instructions say to dump the water out every day and start fresh in the morning. I don't do that, because I am too lazy.