Give them at least a day on replies. Most of mine have taken 12-24 hours for a reply.
My first support email to them was #3xxx back in June. My request to return was #18xxx a few days ago. Those emails were about 12 weeks apart. That puts them at around 150 to 200 new support requests per day, plus multiple emails for each request if a reply or multiple replies are made by each end of the chain. Divide that into however many employees they have, subtract weekends and holidays, and you'll understand why it takes them time to reply.
That's not an excuse, mind you... just some interesting math.
Also note that support requests aren't necessarily returns but would include order status requests, new ideas, bug submissions, review requests, etc. "Under water" is an understatement.