We keep up to a stick in a ceramic dish on the countertop (and like a previous poster, "up to" often means a mere sliver, left there by DF or his 11 y.o. son), the rest of the pound in the fridge, and I try to keep a pound or two in the freezer. Unless I know I am going to be doing a lot of baking, I just buy salted and use it for everything, and reduce the salt in my cooking a smidge to compensate.
I probably eat the least butter of the three of us, so I don't really pay a lot of attention to how quickly we go through it. I feel like it has to take us at least a week to get through a stick though, and I've never known one to go off. Every so often we'll throw a bit away because it's gotten bread crumbs in it, or it's melted and recongealed, or it just generally looks unappealing. We live in South Carolina, the house stays at low-mid 60s in the winter, and upper 70s in the summer.