Creating a stream of the same object between two points in AE?
One possibility is to move a single object along a path (an asterisk in the example shown), using some position keyframes.  

Then place an adjustment layer above the object, with an Echo effect on it.  

Weirdly the delay in seconds needs to be a negative number, adjust to get the distance between the repeating objects that you need, then increase the number of echoes for as long as you need the effect to last.  

It won't create a perfect loop, but you could do that afterwards by adjusting the timing of the echoes, and the start/end points of your comp as described in this answer.