How to Ask Questions of the Form:'how long have you (been)...?

Here are clear examples on how to ask questions of the form:'how long have you (been)...?'. Many people often mistakes when trying to ask questions in this form.
  • How long have they been married?
  • How long have they had their car? (Don't use do they)
  • How long have you been driving? 'Since I was 20'.
  • How long have you known Jane? (Don't use have you been knowing)
  • How long have you been working / have you worked here?