You're right Jason.
Ok, sorry, I was on another level.
Some of the Anti-Wear additives "shear-off" and some go back into solution. Some of the original additive components "decompose" never more to help with Anti-Wear. A small fraction of the decomposition process is that of evaporization.
Let's take ZDDP for example. It is made up of zinc, sulfur, and phosphor molecules. The sulfur helps the zinc and phosphorus "bond" to the metal, creating the multilayer film. The zinc films will melt at high temp or pressure, creating the plastic layer. The phosphor molecules contribute to the EP properties and allow more "slip and slide" when high pressures are present.
Mechanical shear will tend to "scrape" some of the molecules off the surface. High temperatures will cause evaporation (decomposition) of some of the sulfur and phosphorous molecules. When the zinc is sheard from the films, some of it just goes into the oil and never "rebonds" to the metal; it doesn't hurt anything, in fact zinc is a "base" metal helps to control tbn somewhat and keep acids under control.
Now some of the sulfur and phosphorus that don't decompose as evaporates, turn into acids when combined with moisture. However, these acids are very mild and are very often neutralized by the calcium, magnesium, and moly (if present).
Jason is correct, zinc will still show up in an analysis, even though a small percentage of the zinc is just floating around not doing much, kinda like me when I'm swimming at the YMCA.