Hello tabish1987,
We see you have some questions about the Apple Trade-in process, and we can help out.
This page here has a good deal of info, including a helpful Frequently Asked Questions (FAQs) section: Apple Trade In
In the FAQs section it'll note the following: "Keep in mind that the estimated trade-in value is valid for 14 days, and we encourage you to send the device to us within this time frame to ensure that you get this value."
If you may not be home until late December, you may need to re-initiate the trade-in around that time. You can also opt to trade the device in to a local Apple Store, if possible: Find Locations
If you're trading it in as part of the process to receive credit off of a purchase, instead of a gift card, then you may wish to reach out to Apple's sales specialists: Contacting Apple
Be sure to choose your country from the dropdown box at the top, if it presents itself, to get the most accurate contact info for your region.
Cheer.s