Can I update the next ship date? Say from December 25th to December 20th?

Yes! Just log in to your account and visit the "Auto-Ship" section of your account. Then on the right hand side of the subscription you are trying to update the frequency for, click the "Edit" drop down and select "Edit Frequency or Renew Date". Choose a new next ship date and click save. Your subscription will now renew on this new date.

Please note: If you need to change the frequency, do this as well. Changing the next ship date will not update the frequency if you do not change it yourself.