My current knowledge is Wellbutrin (bupriopion) XL which is said to be actually roughly 24 hrs

That is the extent of my knowkedge or understanding of the longest-acting I am [currently] aware of.

I believe there is a newer ADHD med that is like tri-Adderall (16-18 hours) but I am not confident in those figures since that is not available in my country nor would I likely self-advocate to be prescribed such a long-acting substance