I have figured that it's realy the length of the page but not the number of char.
For the same text with a windows open to half the size of my screen no freeze/crash even when scroll to the end, but if i reduce the windows and scroll again then freeze and boum.
For the same text with a windows open to half the size of my screen no freeze/crash even when scroll to the end, but if i reduce the windows and scroll again then freeze and boum.