Another question about sponsorship of parents

[kaveh.mahdian]

I want to sponsor my parents. I have a borther who is dependant on my parents and he is 20 years old. He is studying at the university
to get a bachelors degree. I know that if he contines his studies he will be eligible to be in the file until he studies. But my question is
if any time he finishes his studies he will be out of the file or just the starting period of application is important?
Thanks,