How often是疑问词，后面加一般疑问句，就是陈述句的助动词提前。
例句
How often do you go to the theatre?
你多长时间看一次戏？
How often do you go to the theatre ?
你多久看一次戏？
How often should I do exercise?
我应该多久运动一次？
How often do you do housework?
你多长时间做一次家务？
How often do you take exercise?
你多久锻炼一次？
林业动态信息
