What do caffeine withdrawals have to do with hunger? Increased sensitivity to adenosine will slower the conversion of dopamine to norepinephrine; thereby, jacking up dopamine levels - making you sleepy. Moreover, increased sensitivity to adenosine happens unformally, meaning it doesn't shorten the half-life of caffeine, it just takes more caffeine to get the same effect. After all, one capsule has less caffeine in it than your typical cup of coffee.
I never correlated caffeine withdrawl with hunger...but caffeine itself is an appetite suppressant. As are pretty much any stimulant. And yea, when caffeine consumption is decreased or discontinued, increased hunger is quite common. As you develop tolerance to the drug, the anorectic effects dissipate as well. I thought that this was pretty well established. Not sure what that has to do with half life either.
Additionally, there's a lot more to dopamine than making you sleepy. In fact, drugs that increase dopamine activity (amphetamine, cocaine, methylphenidate, etc) usually have the exact opposite effect. It is often coined the "reward neurotransmitter" and its activity is a major reason that many of these drugs cause the euphoria and addiction potential.
I'm also not quite understanding where this glycogen depletion in 3 days is coming from. Generally, the body stores enough glycogen to last for 1-2 days. Glycogen is made from sugars being stored in the bloodstream. As stores begin to deplete, cortisol is released, making sugars from proteins to ease the lost rate of glycogen. Naturally, glycogen should function as an exponential decay, but this neglects a rather important variable: the times and quantities when the user does eat. This should be a piecewise/staircase function, operating on an unknown variable which would lengthen the duration before these effects are experienced and probably also explain why others can feel these exact same effects within their first week, or several weeks after. Lastly, this glycogen theory would be a more reasonable explanation as to why drinking simple sugars can barrel through the loss of effects early on in the day.
I'm not sure where u got the 3 day figure, as I never said that in my post. Liver glycogen stores can be depleted almost entirely within a few hours of exercise. For someone in a calorie deficit, and exercising regularly, as most SX users on this board are...this will take much less time than the 3 weeks you mentioned earlier. Those that are using a low carb or zero carb diet will deplete glycogen stores extremely quickly. At this point, they will switch over to ketosis and use ketone bodies in place of glucose to fuel the brain.
Glycogen is not stored in the bloodstream, as you stated above, its stored in the liver and skeletal muscle. The glycogen of concern in this discussion is that stored in the liver, as that stored in skeletal muscle is not really utilized for gluconeogenesis to supply other tissues. This is the job of liver glycogen. If the decreased effects of SX were due to liver glycogen depletion, it would happen much sooner than 3 weeks in.
This loss of effects due to tolerance happens with any stimulant drug. I don't see why anyone would think that SX is different. It is the most logical explaination for what this user is experiencing. As one of my pathology instructors once said "when you hear hoofbeats, think horses...not zebras". In other words, the most likely explaination is usually the right one.
Sure, some of the lethargy people are experiencing is probably due to low blood glucose...but hell, this happens when you're dieting no matter what you are taking. What was described above sounds much, much more like drug tolerance.
It's definitely not just one thing that's causing the effects, but I don't believe caffeine to be what's topping the chart. Onset accumulation of adenosine is, however, a probable contributing culprit. After all, that is the byproduct of energy consumption. ATP eventually degrades to adenosine. In the event you are burning so many calories that you've lost into the double digits within your first two weeks, there's a lot of adenosine being formed.
I don't believe its the caffeine either. Its whatever the main SX active is. I just used caffeine as an example.
It's understandable that people don't buy the hype...until they get a sample and know it for themselves. 
