The longest time to wear a weave or hair extension (meaning that it is a sew in) is between 8-10 weeks. Leaving a weave in too long can cause you not to take care of your own hair correctly and possibly cause damage to your natural hair. Remember, when you remove your hair extension, you may think you are experiencing heavy hair loss, but the reality is that you are just removing days/weeks of shedded hair that could not be removed with your hair extensions on.