If you are a teenager, you should wear circle contacts as less as you can. As your eyes are not fully develop yet. Colored with poor quality may make you suffer from some diseases, such as cornea anoxia and dry eye, and they may also narrow your vision field. But if you really want to wear them, it would lees than 12 hours. If you wear them longer, you may feel sore, tired, and this could cause keratoconjunctivitis, trachoma or even lose your sight.
We all know contact lenses are not good for our eye health. There is a main reason that contributes to how long you can wear the contact lenses. Our eyes need oxygen to keep healthy. Different materials of contact lenses can allow different amount of oxygen to go through. This makes different types of lenses acceptable for longer time. Generally, I advise you to wear contact lenses such as circle contact lenses no more 8 hours a day. Meanwhile, you should try to choose the material which can let more oxygen go though.
Circle contact lenses are gorgeous and I support wearing them , but you also should pay attention to the risks. Circle lenses are worse than normal contact lenses because they have the pattern on them. Bad things will happen! If your circle lens seller is not telling you about the risks and how long you can wear, then you should definitely move onto someone else. Circle lenses are not made to be worn for an extended period of time, you should only wear them for 4-6 hours a day. Most wearers put the max at 8 hours, but please don't go over 8. I would stay between 4-6 hours.