Rant: Why does coordinating Christmas take this long?

It's SEPTEMBER and my ex is already asking about Christmas plans. We've done the split for 3 years but apparently last year when I had the kids Christmas eve and she had Christmas day isn't good anymore. She wants me to take them Christmas eve to Christmas morning, then give them up for two weeks. Nope. Not happening. I have every other Christmas per the custody agreement and this year is MY year. Why does she always try to negotiate in September when we literally have a signed court order??