It depends primarily on the quality of hair extensions that you have been asked, but good hair extensions properly maintained can last up to 5 months. Note that in general, the basic extensions last 2 months, but you must return frequently to your hairdresser: Almost every month, a visit will be required to withdraw the small hair that would be taken in the keratin.
It is obvious that with hair extensions require more care. You do not need to change the range of shampoo, but you have to hand washed your hair frequently (3 times per week). Do not forget to make hair masks at least once a week. In addition, brush your hair regularly, using a brush specially designed to prevent the formation of knots.
You should know that hair extensions are not safe for your hair. The concern is that the bits added suffocate your hair like parasites. Less oxygenated, your hair is fragile, damaged and when you remove the hair extensions is often a disaster. Prefer the addition of a few strands to give your hair thickness, rather than the locks on all of your hair. Hair extensions are cost around 5 € per wick. However, prices are very variable depending on the hair, and can go up to 1500 Euros. In all cases, it is best to request a free quote through your hairdresser.