The lessened effect is due to your body getting used to having increased levels of dopamine and norepinephrine, so stops producing as much.

The fact that the medication is out doesn't make your dopaminergic system more sensitive by itself. It might take a while.

I've been on the medications for almost a decade now, so when I take a weekend off, then I am basically useless by Monday when I start them again. I swear it takes days from them to start working again every time I take a break.

So, my dopaminergic system probably has holes burned through it.

Yes, I have certainly noticed it takes a few days for the full effect to ramp up as well. And there seems to be residual effect for about 12 hours after the last dose, though in general the peak effect lasts about 4 hours for me (on lisdexamphetamine)