How long do bonito flakes last once opened?

Excuse me, I was wondering if you could shed some light on the shelf life of bonito flakes once they've been opened. I've heard that they can lose their flavor and aroma quite quickly if not stored properly, but I'm not sure exactly how long I can expect them to last. Do they need to be refrigerated or can they be kept at room temperature? Is there a general rule of thumb for determining when they've gone past their prime? I'd appreciate any advice you can offer on how to ensure my bonito flakes stay fresh and flavorful for as long as possible.