I use actors for the parallex background effect, and i'm getting a good performance.
Each actor (background) has a speed directly related with the main character's speed, something like (negate((characters speed)/4)) something like that.
Those actors are anchored to the screen, and once they are out of the screen they go back to the origin point.
How do I repeat the background while it's moving, to cover the blank spaces? I use the drawimage option, to copy itself to the right or left depending to where the main character is moving.
The drawimage option is great to repeat backgrounds since it takes far less memory than putting 1,2 or 3 actors more.
and the effect is pretty cool, I will post a video of the game im working in.