In Back to the Future 2, Marty gets fired for doing something illegal. Several notes reading "you're fired!" were faxed to him. At the end of Back to the Future 3, Marty avoids the car crash and thus the words fade away.
Wouldn't it have faded away when 2015 Biff changed the timeline in 1955? Biff's changes meant that Marty never ended up working for Needles, so why didn't the note fade immediately?