always是频度最高的词，表示动作的重复，状态的继续，中间没有间断。

often意为“经常、常常”，不如usually那么频繁，表示动作重复，中间有间断。

相关介绍

Work always piles up at the end of the year.

年底总是积压一大堆工作。

There's always a lot of traffic at this time of day.

每天这个时候总是有很多来往车辆。

This kind of question often appears in the exam.

这类问题在考试中经常出现。

As often as not, he's late for work.

他上班往往迟到。