I understand - it's the same for me.
I haven't found any way to keep effects consistent - just like for you, and many others, most drugs only seem to work for a limited time - a few days at most.
This is sometimes called the "honey-moon effect" among some other types of patients as well - we can't be sure if this is REALLY an effect though - it could just as easily be simple hypomania/euphoria which many different type of people get initially from drugs - euphoria is a lie, and not real efficacy.
It could also just as easily be PLACEBO, i.e we WANT the drugs to work so badly, that for a short while, they do.
Upon closer inspection, I think I've had this kind of honeymoon-effect from nearly every drug I've ever used...
All I can say is that you need to try the drugs and see what happens... not even Professor Russell Barkley, the person who knows the most about SCT, can say what will work - that's why he's often vague and careful in his wording when he talks about treatment.