I think it depends on where you live and if you have cats! I grew up in the southern US and we always refrigerated our butter because it would melt into a pool of goo if we left it out in summer. We just got in the year-round habit. My mom now lives in Colorado where it can get over 100 degrees in summer, so she refrigerates. But I now live in New England and leave my butter out all the time because otherwise it's unspreadable. I store unused sticks in the refrig until I need them but usually keep a stick in a covered butter dish on the counter. Also, when I had cats, I could never find a butter dish that would keep them out, so I tended to put it in the refrig.