I got an 20x4 I2C LCD and it is my first time using one, so I tried the Serial display example and at first it seemed to work fine until I entered more than 20 characters. I enter "1111111111111111111122222222222222222222" and I get this.
you could put your own wrapper around lcd.write so that when it hits character number 21, it does a setpos followed by the characters until it hits the next end-point, the setpos again etc