I think turn around times depend on the quantity purchased, and how long it takes for you. Give them a maximum time.. or a time window. For my candles, I say 3-4 weeks for large orders.
I request full payment for wholesale orders. Since margins are lower, I need it all so I can purchase supplies. I also don't want to be stuck with any product if they make changes.. if not paid in full your customer may not feel like they have to end up buying everything. I used to own a shop, and I always think back to that. Even if I was buying products from a regular catalog company, I would have to pay up-front and wait for a few weeks!