I did do my own center pieces.
While I did not ship them I brought them with me when I arrived in Disney (I live 2 hrs away), so I was able to drop them off 2 days before the wedding.
Disney set them up for me.
I HIGHLY Recommend that if there is a special way to set them up include directions when you have them delivered or dropped off to dis floral.
We had glass cylinders with a light cube filled with glass marbles and it was supposed to be filled with water.
Well they set it all up but they never put the water in.
I didn't even notice till late in the wedding, so I was a little peeved but it wasn't the end of the world.
If you are going to mail, you don't want them getting there so far in advance because they could get miss placed in the warehouse.
I say no more than a few days.