The first time I ever ordered from NGK, the order took something like 27 days to get here (via USPS Priority Mail). I asked Mike about it and even though I told him not to worry about it (it had only been a week or so at that point), he took it upon himself to contact the post office and try to hunt the package down. He was pretty diligent in his efforts and The package eventually showed up of its own accord (without any help or explanation from the P.O.), but I appreciated the fact that Mike went the extra mile for me without even knowing me and since then I have had many problem-free transactions with NGK.
The thing that saves you is that there should be a tracking number attached to a UPS shipment. If it was first class mail without any sort of number attached to it, then you'd just have to sit around and hope that it showed up.