I put my employer's eBay store into "holiday mode", and extended the handling time to 15 business days. This easily covered the period we had off.

But, yes - mid-way through the holiday break we had a buyer send a frosty e-mail demanding to know why it was taking so long to despatch the item. I sent an equally frosty e-mail including screen-caps of the "This seller is away until..." banner and the 15 day handling time. 

And on Monday - a buyer purchases an item and pays. Then immediately sends a message saying they want to cancel the order as the 15 day handling time is excessive.

You can't win...