According to international celebrity hair stylist, Marco Aldany, if you are making your hair darker then it is fine to dye your hair this regularly. Your hair is porous and hair dye fills these holes and coats each strand. He added that it is best to use hair dye with no oxidants as this strips the hair.

But if you are lightening your hair then you are stripping your hair and this makes it weaker. So Marco recommends that you take a break of about a month and a half between each colour treatment. He also suggests you use products to protect highlighted hair.
 
This was asked by Precious Fedi.