Mastering it? At least 10 years.
Being proficient enough to develop complex apps? In about 1-2 years depending how many hours you put in, and how quickly you learn since everyone is different.
wel, there goes half the students walking out the door…LOL
<< insert funny gif of half the class walking out the door here >>
It’s job security. These are great paying jobs because it isn’t easy and it takes a lot of work. If this were easy, everyone would do it and it would pay minimum wage.