I have always kept butter in a butter dish that stands on the kitchen counter, as butter kept in the fridge is too cold to spread.
Right now, I have a Le Creuset butter dish with lid, but previously, I had a cheap plastic one, which was equally as good, as far as keeping butter fresh, and had the added advantage that a butter loving cat could not get the lid off, as it had a rubber seal.
Now that I am alone, 200 g of butter last for a week at least, and more often for ten days, and is perfectly fresh at the end of that time.