Answer:
They stay in the area in which they were initially deposited for a relatively long time because they are not free to move about the insulator.
Step-by-step explanation:
If we place large number of electrons in a small area of an insulating surface then the charges will remain in their place for a longer period of time because the charges do not get a path to flow despite the repulsion between them.
Insulators do not have conducting electrons free to carry the charges apart from each other whereas the metal have a sea of electrons free for the conduction of charges.