Should I always use this breakpoints?

In addition to Ryan's reply, I found this article really helpfull on when and where to use breakpoints: http://bradfrost.com/blog/post/7-habits-of-highly-effective-media-queries/

Especially the advice: "Start with the small screen first, then expand until it looks like shit. Time for a breakpoint!"

It basically tells you not to focus on different devices and their screens when designing a responsive lay-out. Right now webpages are mostly viewed on smartphones, tablets and desktops, but what about next year? And the year after that? Popular devices change, screen resolutions change. You can't go around updating your website everytime someone presents a new phone with a higher resolution screen. Or worse: a completely new device with a proper browser.

Instead, focus on the content you're displaying. Does it look good at a particular size? Then good! Does it look like crap? Then add a breakpoint and change some things around. No matter what the 'it device' of the near future might be, this'll keep the website displaying properly.

Not necessarily, those three points are chosen because they are commonly used for three basic media devices: desktop, tablet, and phone. These points may change in the future, and may even vary now depending on the pixilation of common devices being put out into the market.

They are probably good to use most of the time but not necessarily forever.

Hope that helps!