What's the shelf-life of this recipe?

Hello, Julianna! It's just roasted fat, so it will last about 3 weeks in the fridge. Indefinitely in the freezer.

I don't know. But you could try emailing the author. If you click on her name under the headline of the recipe (https://food52.com/recipes/31896-roasted-and-whipped-bone-marrow), it will take you to her profile page. Then click on the little envelope / email icon to send a message to her.