Thank you very much for that novella. It finally allowed me to see why you are posting the type advice that you are. And I must say if cell phones ever start using "commercial grade" Lithium-Ion battery packs, your advice will be invaluable and even I will follow it to a "T".
But at present cell phones are using "consumer grade" single cell 4.2V Lithium-Ion batteries. Now to be fair, your advice will in fact allow the battery to "chemically" last longer. It will take the average life of 2 to 3 years and extend it out to probably 8 to 10 years. If, and this is a BIG IF, the user doesn't charge the battery frequently. But because your advice never allows the battery to reach full saturation, the 25% to 75%, you suggested, operational range provides a very fixed amount of milliamp hours of usage. This in turns leads to more frequent charging cycles being required. And this is where you advice actually causes a major issue and can cause the battery to fail much sooner than your advice intended.
Now to explain this I actually have to bore the general audience with some chemistry. But the side benefit is, it will help you understand why I used the shortened phrase 'depletion of the electrons or "stored energy"' that you took issue with. The proper version of that is technically 'depletion of the electrons potential or "stored energy"'. I apologize for dropping that word out. At the time I didn't think it would be needed. But alas it now is. BTW; my memory is a little rusty on this so forgive me if I gloss over some of the finer points. It has been over 26 years since I did serious chemistry work.
One of several Lithium salts compounds, decided on by the manufacturer of the battery, are used as the basis for making a Lithium-Ion battery. The basic pretense is to use an electrical current to pass thru a piece of graphite combined with a Lithium substrate to starts a chemical reaction with the Lithium salt compound. This electrical current causes the outer electron shell, the valance electrons, of the Lithium substrate to become "excited". These valance electrons basically start looking around for other elements to bond with. The stronger the current to the battery, the faster the Lithium valance electrons pick up the current or charge. This then starts the chemical reaction of bonding with the Lithium Ion salt. Now the new chemical compound that is created is not technically "stable". If it was, then we would never be able to get the stored energy back out. So as soon as we put this battery into a circuit it does it very best to release the stored energy by reversing the process. And hence why I used the phrase I did. The electrons potential is passed from wall charger to the battery and then finally to the device.
Now during that process is where your advice has the very serious potential to cause a major problem to a "consumer grade" battery. BUT I freely admit is 100% applicable to "commercial grade" Lithium-Ion batteries.
This entire chemical process has a "bad" side effect. While the charging cycle is occurring, the graphite and lithium substrate expand in size. And as soon as we remove the charging current it contracts back to its normal "at rest" size. If that expansion and contraction occurs enough times, you will crack the graphite. Once the graphite becomes damaged, you can no longer charge the battery.
Now the Depth of Discharge chart is based on the Lithium Salt chemically changing state over time , IE why 500 full cycle charges and you end up with less storage capacity. So your advice is some what spot on that regards. You are trying to prolong the Lithium Salt compound. But your advice accelerates the demise of the graphite.
Also the amount of current directly correlates to the expansion of the graphite and lithium substrate. So the four stage charging chart can now be used to show how we can reduce the damage to this critical graphite. As the current drops the graphite shrinks back to normal size. And physically you always want to slowly allow graphite to return to its normal "at rest" size vs what you suggest which is cutting off the current while still in Stage 1 and at 100% amperage. You are basically introducing the worst case scenario to the graphite.
I apologize for not stating any of this sooner, but to be blunt, I didn't realize you were applying "commercial grade" advice to "consumer grade" single cell batteries till now. Plus I thought you would have known all of this based on the amount of data you had been referencing.
So to wrap this up, the average consumer, should probably stick with the general advice I have been giving for years. Let the battery discharge to 40% and then recharge back to 100%. Try to do it only once a day and the battery will last for the two years you own the device.