How old are they when they can give up a night light?

Ten year old is trying to quit but had a relapse. See no end in sight with the 7 year old.
Saying I never should’ve let them have one in the first place isn’t helpful because, well, I did.
okay, okay, it’s more than a nightlight. It’s a closet light with the door open partway. [...] http://bit.ly/9jhYfb