Just wanted to update this thread with my experience in case someone stumbles upon it:
I mailed two packages with delivery confirmation and tracked it via usps. I did not receive email confirmation from H.com that my items were in the process of return until 5 days after they were received. Two days after I received the email I noticed that the charges were refunded to my credit card, and they even refunded the full amount of the shipping charges even though I kept other items in the same order. This was nice because I once exchanged an online item in a boutique and wasn't credited the shipping charge.
It's also possible to look in your H.com online profile at what has been returned and refunded under "Your Orders" (you have to click on the individual orders) but this option was not available until after my refund had already posted to my credit card. All in all, it seems to be about the same experience as BHmommy. If any of you experience otherwise (longer delays), please let us know what region you're in and what seems to be normal processing time for you.
HTH someone out there! (Though, I'm sure the same info is buried somewhere else on this site!)