I store pan drippings ( with bits of whatever was cooked in it) in the fridge up to a week. To clarify any animal fat you heat it until clear, and carefully strain out any bits in it, and you may need to do it more than once. When chilled it can last weeks in the fridge IF you got everything...
170 f is recommended for most poultry, but most chefs rarely go past 135-140 f for duck or geese, any more and they’ll be tough because though the skin is fatty the meat has little fat inside, and you don’t want to cook out those yummy juices.
I guess it comes down to trusting the person who...
Rendered duck fat has endless uses, particularly in French cuisine there are a ton of recipes that use it. Use a meat thermometer and be sure NOT to overcook it, duck should be dark and a little bloody when done, like lamb