Are you going to cross wire the foundation? If not, I wouldn't do it more than a few days prior. With foundation, I would worry about melting, warping, and mice more than moths.
Having said that, I have a new hive setting in my shop without cross wires. It has been there two years and is still in good shape. I didn't do it purposely, but it did happen and is still fine. The sooner before using, the less chance for Murphy to step in and let something happen.