If you leave butter out in a dish for that long, you will get mice, or the neighbour's cat, taking care of it long before eight years. Or worse, raccoons. They don't get those bulky bodies by ignoring free fats.
Speaking of cats and butter...My mom was gifted a nice butter dish with a lid from her father. My family's cat, Frank, licked and pushed the heavy butter dish from the center of the table to the edge where it fell and broke. So yeah. No butter dish is going to last eight years in my house.