It really depends. I had to wait about 2 weeks for items that weren't high end. However, luxury products appear to be faster. I had to wait about 1 week for that. The one time I was sent the wrong item (Pure Wand instead of Eleven) they sent me the right item overnighted before I could even mail out the other package.
I've had two experiences. One was replaced within a week. The second was never replaced, and when I followed up two months later, they found the record of the received return almost immediately, and made an immediate refund.