how soon 过多久,答语用：in+一段时间
how long多久,答语用：For+一段时间,since+时间点
how often 多久一次,答语用 Once/Twice a week.‘一周一次/两次
How soon will you leave for Beijing?
In a week.
How long do you stay at home every week?
For two days.
How often do you go home?
Once a week./ Once a month.