How long is 5 mg of Adderall effective?

I'M a 25 year old female and have been on and off Adderall ( due to insurance coverage/ being too thin) since I was 6. I am still to this day finding that I do need it and that it still help me tremendously. I have a severe case of Adhd (now that I'm older It's just ADD...for the most part). When i was young I was on both adderall and Ritalin. When i was around 16 they me on 2 30 mg xr per day. I'm currently taking 20 mg xr and i have a feeling that I'll have to bump up the mg's again in the near future. The Dr.'s always used to tell me that most children grow out of it in adulthood. I on the other hand was not one of those lucky people. I will most likely be on adderall for the rest of my life (insurance willing of course). It's just something we have to learn to live with. It could always be worse. Only time will tell for you child. Everyone is different. I wish you the best of luck!