How long has it been since you spoke to [name of person]?
How long is it since you spoke to [name]?
How long did you go without speaking to anyone? (This would suggest that someone has for some reason not spoken to a single person for quite some time!)
How long did you not speak to your boyfriend for? (If a couple have an argument and the woman decides to stop speaking to her boyfriend, someone might ask her how long that situation lasted.)
You might hear people say something like "How long haven't you smoked for?", if someone has given up smoking, but a better question would be "How long ago did you give up smoking?" or "When did you quit smoking?"
Student or Learner