As long as you've kept the leftover turkey refrigerated you can eat the leftover turkey for up to 5 days before it goes bad.
You can keep the leftover turkey longer than 5 days by freezing the leftover cooked turkey and when you do you can save the leftover cooked turkey in the freezer for up to a year before it goes bad.
So if you have any leftover turkey and don't plan to eat it within 5 days you should freeze the leftover turkey and it will last a lot longer.
I usually eat any leftover turkey from Thanksgiving or Christmas within a month or so after but sometimes I'll eat it sooner.
I always just freeze any leftover turkey or other meats so I can keep it a long time without worrying about it going bad.