trade-in refund time limit

We are all other users here, so we cannot speak for Apple. I searched to see if I could find anything, but could not. Here is the only thing, so I'd suggest contacting Apple - possibly do a chat with someone at the Apple store to see if an extension may be offered.

You should speak with Apple, but my understanding is if you want the trade value take off your purchase of the new iPhone, it would have to be received within 14 days of receipt of the new iPhone. You're right that if this is a holiday gift, you won't have the opportunity to return the trade until after the holidays. In that case, you will have missed the 14 days after receipt of the new iPhone, so instead of getting the credit taken off the price of the new iPhone, you can return the phone to Apple directly and you'll receive an Apple Gift Card for the value of the trade.