How often表示频度,意思是“多久一次”.例如：
I go home once a week.——How often do you go home?
试比较：
How soon表示时间,意思是“多久以后”.例如：
I will go home in two days.——How soon do you go home?
How long表示时间,意思是“多久,多长时间”.例如：
He worked here for two years.——How long did he work here?