Too may variables guys. What are you using for a solvent, PEG400, PEG300, some type of oil? What are the solutes, MDHT, M1-Test, SuperD Powder, 1,4AD.......
Different solutes are going to have different half lives in various solvents. And then, is it really an oral solution per you thread title, or is it a suspension? Suspensions will typically last a lot longer.