The length of time you take a supplement is a conversation between you and your doctor. As of yet, there haven’t been any studies suggesting long-term use of joint supplements causes health problems. (There also haven’t been many studies looking at joint supplements over the long term.) The primary study that looked at long-term joint supplement use suggests that you get the most benefits by 18 weeks and then maintain those benefits. There's no reason to stop if there’s no undue financial burden and you don’t feel any negative side effects.