Check close to the end of Dec on blackout dates. Some years they won't guarantee delivery after the 18, 19, 20th. I don't know how it's determined and it may be a local policy.

Other than the blackout, I've shipped stuff and LOVE the discount! Walk in with a 'bookbox' size box that weighs 9-10 lbs (clothes and presents) and walk out with a tracking number for $10-$15.