☐ Why Wait to Degauss Again?

Why does pretty much every document that mentions the deguass function of monitors tell you to wait about 15 minutes before degaussing again? Does this mean that you must also wait around 15 minutes before turning off/on a monitor that automatically degausses when turned on.

Speaking of degaussing, what happens if a monitor is exposed to a magnetic field that is stronger than that created by the degaussing mechanism? Do you need to use a more powerful, external degausser, or will it be fixed over time because the degausser reduces the deviation by a bit each time it runs, until the deviation is within the degausser’s normal fixable range?