In my opinion, it is easyer to use the LiteTween plugin.
But, that is not your qeustion. So, let me try to give a good answer.
First of, i am aware that mostly lerp gets used with a dynamic start point, a static endpoint and a static lerpfactor. A lerpfactor that has to be dt corrected. And that is not really easy.
This way the next step gets smaller and smaller (but never zero), giving some (in my eyes fake) feeling of smoothing out. But, you will have to when the target is moving. That is (if i understand right) not you case.
So, under the condition that the target is not moving, lerp can be used in much (again in my eyes) better way.
Basically using a static start, a static end and a dynamic lerp factor (that is already dt corrected in the right way)
Besides that. there is not only lerp, but also qarp and (very usefull) there is cubic.
In this example i use cubic to easy-in and easy-out a movement. I kept it as 'visual' and as 'simple' as possible.
Look at the imagepoints on the ruler.
https://drive.google.com/open?id=0B1SSu ... nZReFFzWEU
Hope this opens your eyes to new ways. Greetings.