The legendary Jeremy Keith, talking about best practices for responsive web design:
And here’s the key: try to come up with as few major breakpoints as possible. That might sound crazy, since we’re talking about responsive design. After all, we have media queries, so let’s use about 12 of them, right? No! If a linear layout works for every screen and is appropriate for your particular concept, then there’s no need for different layouts.
I’ve learned this the hard way in my early responsive work; you find writing more and more media queries easy, and next thing you know your responsive code gets out of control. Follow Keith’s advice here; simpler is generally better.