A few reasons it's been that long.

1. Your mailbox is full, so be sure to delete any old mail.

2. High traffic either on a particular item or at the mog station site itself.

3. The mog station might have technical issues on their end.

If none of those are the issue, there's also the Reward/Purchase delivery request on the top window of the moogle mailbox window. It usually works for me if I feel like it's taking awhile for my stuff I buy from the mog station to deliver.