If qualifying for Premium Service badging is not important to you, I would suggest thinking about increasing your handling time.

I post the same day as purchase, or next day if the order is made after about 1-2pm, depending in when I can actually get up to the PO, so I could have a 1 or even 0 day handling time...but I have it at 2 days specifically so that eBay's estimated date of arrival is more realistic. The extra day or two added on to eBay's ETA helps a lot when it comes to people thinking these dates are some kind of due date, and should give you a bit of breathing space - and cut down on the instances of people thinking an item is "late" (or missing) if it's not there by the first date eBay display.