Anonymous wrote:"Hey, put away that Tupperware . . . that's our dinner for tomorrow night, not leftovers for the taking. Thanks for understanding!"
Agree with above.
However, it's normal for old people to be weird. They act on norms and expectations from a long ago time.
At my family's house, my Silent Generation dad gets antsy about freezing some of the turkey leftovers. On Thanksgiving Day evening, he will take a large chunk of the turkey breast or a bowl of turkey meat pieces, put it loose into a plastic freezer bag and put it in the freezer. This is terrible because the meat needs defrosting to use and it usually gets ice crystals on it.
My whole family prefers to eat up the entire turkey as fresh leftovers vs. putting away any. We don't find Dad's ruining of the meat to "save it" helpful at all.
So we basically have to watch Dad every time we get the meat dishes out. And loudly say "Do Not Freeze Any of the Meat!" over and over again.
In your case, I'd just make extra for the in-laws. An even bigger turkey, more mashed potatoes, etc. I'm one of those people who loves ordinary Thanksgiving dinner with dry turkey. So I can kind of understand their weird hoardery urges. Maybe it would help if you made a rule like "No leftover box packing until Saturday". If it's an approved plan by you as the host, then it's okay.