It'll last at room temperature for a couple days, but make sure to keep it covered from air and light. If it's the summer and averaging above 70 in your kitchen, best ot keep it in the fridge. Especially since this is the unsalted kind (salt inhibits bacterial growth).

Also, because it's so rich, it's tough to use in one sitting. If you leave it out, try leaving just 1 oz in a separate tupperware.