Brainwashing as in a weekend of indoctrination doesn’t totally change you overnight. This is why liberals repeat the same dogma from entertainment to academia to news for years.
This is why they have drag queen story times and children’s books on sexual perversion in preschool and demand to have complex lessons on gender fluidity throughout elementary grades.
By the time the kids hit puberty, they’ve heard the same, consistent message from liberals for YEARS.
That’s not brain washing, it is a deliberate imprinting/education process.
There is no time period specified in the definition of "brainwashing." It can last a weekend or a lifetime.
BTW, here is the etymology of the term (for you fellow language freeks)...
Brainwash"attempt to alter or control the thoughts and beliefs of another person against his will by psychological techniques," 1950, a literal translation of Chinese xi nao. A term from the Korean War.
Source: etymonline.com