我爱你一辈子用英文表达为：I love you all my life.

life：

n.生活;生命;人命;性命;人的存活;生物;活物

复数： lives

It was time she put her life in order.

她到了该好好安排自己生活的时候了。

He's got a new woman in his life.

他生活中又有了一个女人。

The effects will last for the whole of his life.

这些将会持续影响他的一生。

In her body a new life was taking form.

一个新的生命在她的体内逐渐形成。

The cost in terms of human life was high.

付出了很大的生命代价。