I lost a sale today (and quite a good one), because after checking out, the customer didn't like the expected delivery date.
This encouraged me to check what the customer is shown when they buy, and I was actually surprised and pleased to see that Ebay quotes "11 to 35 business days" for postage to the USA.
Australia Post quotes a somewhat hopeful 15+ business days, so Ebay is more aligned with the real-world scenario.
I can't believe that I haven't checked this before, but I know my response to "where's my order" will be different now, and slightly less accommodating, knowing that the buyer was told "11 to 35 business days" for delivery when they checked out.