I have found when taking generic adderall that it would be extremely intense after about an hour and continue feeling this way for about 3 hours. Then the medication would begin to lessen in its effect and I would feel a need to take another tablet to "optimize" the effect of the medication... that is, stay in the intense area. I'm a software developer and become extremely productive because of the medication. Eventually though, it will wear you down due to abberant sleep pattern, poor diet, and constantly being wired. I found the medication to make me feel very positive which was helpful when working in a stressful engineering environment. More positive than any anti-depressant could provide. I changed to the extended release and found that it was much more stable over the day, and that there were less negative side effects than the generic adderall such as aggressiveness. I have decided though that this medication is a detriment more than anything else. It's difficult to stop taking, particularly if you keep upping the dose. Initially when you stop, you may feel extremely exhausted and have a difficult time functioning. This includes not giving the medication on the weekend. From my personal experience you should keep the dose consistent. If you are going to continue taking the medication, I highly recommend using the extended release since it is much more stable through the day with less negative side effects. And only buy the brand name XR because the generic XR has been know to have up to 40% medication than the brand name. Also, adderall can have addictive qualities. So, if your son is requesting more, I would be hesitant about upping the dose. Eventually, this medication needs to be eliminated completely.
Regarding the ADHD. I hate to make generalizations, but boys are just hyper and do wacky things. I used to teach music professionally both private and group classes, and during group classes, the girls are so well behaved, and the boys will do things like try to see who can put their foot over the back off their heads... and the girls just sit there quietly watching. So, if your son was diagnosed as ADHD due to his acting as boys do, then really... shame on the doctors and teachers. Sometimes I feel that these medications are to make one more productive, or to keep quiet. Boys seem to need more enforcement of controlling their impulses... to be more disciplined
Lastly, you need to look into diet, particularly how many food items are eaten that have MSG in them. Almost every processed food does. There are a number of different names for MSG to watch out for... you can just google... "different names for MSG" and you'll get for example "natural flavorings"
MSG is categorized as an excitotoxin. Excitotoxins cause the cells in the brain to fire without purpose which can lead to cell exhaustion and death. I think it's not far fetched to say that excitotoxins could be responsible for the lack of ability to focus and so be labeled ADHD. I also believe it's not a far stretch to say that prolonged eating of excitotoxin will lead to neuro-degenrative disorders such as Alzheimer's...
Check out Dr Russell Blaylocks article "Excitotoxins - The Taste That Kills"
I wish you and your son the best