Once permanent hair extentions are fitted, how oftern do you have to revisit the salon?

after getting permanent hair extensions, how regular do you have to keep going back to the salon for Touch ups etc???Once permanent hair extentions are fitted, how oftern do you have to revisit the salon?
If your hair grows at a normal rate and you are keeping conditioner off of the points of contact (helps prevent slipping) you should be able to last 6 weeks to 2 months, depending on the application.