Why do you say modafinil is not for long-term use? I take it 7 times a week, have done so for years and my doctor tells me it's likely that I will be taking it

Why do you say modafinil is not for long-term use? I take it 7 times a week, have done so for years and my doctor tells me it's likely that I will be taking it as long as I need it (in my case: a lifetime, as it's treating a chronic condition).