My experience (had 4 boxes shipped to me, 2 systems sent back) is that the box takes 3-5 days to get to you. It comes from Fort Wayne, Indiana (if you're in the US).
Shipping back to the facility is standard ground, so another 3-5 days, and then once they have it is generally 3-5 days for them to process your system and ship you a new one. When they ship the new one, it's overnighted to you. Total RMA process takes, on average (for me, YMMV), 2-2.5 weeks, and I live within one day ground shipping of the RMA center. Sony will probably fail to send you the proper email with the tracking numbers, as well, so a pro tip is you can go to FedEx.com and track shipment by reference number and put in your service request #, country and your zip code and you can track your package that way.
In my experience over the past three months, Sony's support is a total mess so don't be surprised if you have to call them multiple times before they process a RMA request properly. If you have severe issues getting them to do anything like I did, PM me, I have the direct phone number to the executive of customer service. One call to him will get your problem sorted straight away. That's how I finally had to resolve my issue.
Good luck!