In Junior High School I asked my Science teacher how long a requested research paper needed to be. The very attractive, blonde, blue eyed and very talented recent college graduate simply responded "It's like a girl's skirt;
long enough to cover the subject but short enough to keep it interesting."
This guidance from Ms. Walls was very beneficial, but now not necessarily politically correct. However the concept does apply well to technical questions during interviews and served me well in many other appropriate matters.