as long as的用法：
1、表示条件，意思是“只要”。如:
As long as you tell the truth，I’ll try to help you.
只要你告诉我实情，我会尽力帮助你。
You may take this book away so long as you return it on time.
只要你按时归还，就可以把这本书拿走。
2、表示原因，意思是“既然，由于，因为”。如：
As long as we've driven this far, we might as well go on.
我们既然已经驶得这么远了，就不妨继续前进。
As long as you are going, I'll go too.
既然你要去，那么我也去。
As long as the weather is changeable these days,we’d better get in wheat in time.
由于这几天气候变化无常，我们最好及时把麦收割完。