I leave my butter out all the time. I use a half pint, wide mouth mason jar and lid. The jar holds two sticks, but I usually just put one at a time in, and the rest of the butter stays in the fridge.
I had a butter bell, but I found that the butter would melt out of the cup and fall into the water when the kitchen got too hot. I like the mason jar because the lid keeps the dust and flying critters out.
I just haven't been the same
since that house fell on my sister.