一般现在时表示的经常性动作是指过去、现在和将来都会发生的习惯性动作。即从现在向过去和将来两个方向延伸。例如，I always get up at six in the morning. 过去、现在、将来都是如此。即现在存在着的习惯。

现在完成时表示的习惯是从过去持续到现在的习惯，不考虑将来。习惯可能会延续到将来，可能在现在终止。即截止说话时，一个习惯保持了有多久了。通常需要时间状语表示这个习惯从过去持续到现在有多久。这个时间状语是必须的。例如：I have got up at six in the morning for 30 years. 如果没有这样的时间状语，则现在完成时就只是表示一个动作的完成。I have got up. 

更多表示经常性、习惯性动作的现在完成时例句：（都有持续时间状语）

I have gone to work by bike for 10 years.

He has written for the newspaper all his life.

He has driven this car since 2001.

与现在完成进行时比较：短期的习惯或一次事件持续到现在。持续状语可有可无。

He has been going to work by bike for a week. (汽车坏了，临时骑车上班）

He has been writing for the newspaper （for three months). (为报纸写文章是临时性的）

He has been driving for four hours. (一次事件）

个别动词如work, teach, learn用现在完成时和现在完成进行时后接持续时间状语差别不大，例如：

He has taught/has been teaching in this school for 5 years.

一般现在时的习惯不可以有持续时间状语表示习惯的持续时间。（因为这种习惯的结束是不可预料的，不可能用持续时间度量的。如果要表示一个习惯截止某时刻持续了多久，就必须用完成体。）

He teaches in this school.

He goes to work by bike.

He writes for newspapers.

By the end of next year, he will have taught in this school for 30 years.