Tolerance is proportional to both the amount of drug taken and the frequency of use. Assuming the relationship is somewhat linear, a 1/3 dose would produce roughly 1/3 the tolerance of a normal dose. Basically, if you took 1/3 dose one day and 1/3 dose the next, you would likely have a dramatic reduction of effects. Furthermore, if you took 1/3 dose one day and a full dose the next, the full dose would be only slightly less potent than if you didn't take the 1/3 dose the day before.
This just seems like common sense, I have taken two or three hits on consecutive days and after the first two, the third dose produces little to no effects at all, let alone visuals.
Also, IMO sugar cubes are the best way to get ripped off, or better yet sold something other than acid. Try find some blotter instead. For most drugs it is damn near impossible to fit an active dose on a little piece of paper. Thats why it is so great for distributing acid. LSD is extremely potent, requiring only 100s of micrograms. This is why it is one of the only drugs to be sold on blotter.