Bundle Star batteries for Canon overall are good!

My son and I are very interested amateur photographers and constantly on the move to find good locations. I have a Canon EOS 1100D and my son - naturally better - a Canon EOS 600D! 1 1/2 years ago, I have already acquired a second battery of Bundle Star for my Canon. The holding of all and holding through. I was in the US and the battery has persevered. For me there is no difference from the original; except .... The price! Bundle Star is really cheap.
My son has been a year, the Canon EOS 600D and the second battery (as a supplement to the original). There were no problems and no lower runtimes. Now he has bought a second bundle Star battery from pocket money, because he was and is good and affordable for him.
What do you actually need 3 battery (original + 2)?
Our son needs! The photographs and films almost around the clock!
A good choice!