After I open a jar of anchovies how do I store it, and how long can they be stored?

I think the answer depends on the type of product. Is it a jar with oil? or Salted dried ones in a jar?

I pretty much always have a jar in the fridge - covered with olive oil, I've had no problem keeping them a month or longer.

I should say that that they don't last that long because we eat them up, not because they go bad... sorry for the lack of clarity.

We keep ours for up to a month in the frig, tho they rarely last that long.

I love Boulangere's idea about freezing them. Since the anchovies are already salted, we usually put them in a jar, with the label from the tin taped to it. We've kept them from 3 weeks to a month and they're just fine. In fact, we have some in the fridge now!

As Denae Peters recommends, definitely refrigerate after opening. If you're not going to use them up soon, say within a week, spread them out in a ziplock bag and freeze them so you can pull out as many as you need at a time to thaw and use.

You should refrigerate once opened and try to use within 2-3 days. Normally, I just start adding them to everything I'm making so they never quite make it to the 3rd! :)