I will chime in here. Professionally, I have BS and MS degrees in chemistry and worked with polymers (plastics and such) for many years. I have not tried this protocol on my own cases that are yellowed yet, because I am just getting back into my old system while teaching my son some computer programming skills (what a great system for teaching programming
IMHO, the chemistry that is presented is valid for the mechanism of the "ageing/yellowing" phenomenon and how to reverse it.
When using the materials described be aware that if you don't follow the protocol TO THE LETTER you are out on your own and working with some potent chemical materials and can not be certain of the results you will obtain. I will reiterate what others have said, concentrated hydrogen peroxide is an EXTREMELY powerful oxidizing agent and can cause burns to the skin (I know from first hand experience), explosions when mixed with reducing agents (think rocket fuel), or damage to other materials it comes in contact with.
The 2% hydrogen peroxide you get at the pharmacy is not concentrated enough to accomplish this reaction. You need to use concentrations in the 12-15% range. You can start with the peroxide available at a beauty supply for bleaching hair but be careful to dilute it properly. If you do not know how to calculate the dilution ask for help! And "if a little is good, more must be better" DOES NOT apply here. The purpose of the EDTA from the Oxy is to act as a catalyst. A catalyst is an agent in a chemical reaction that reduces the energy required to get the reaction going. You want the catalyst to be "pushing" the reaction, not excess concentration of the peroxide. That is the beauty of the protocol developed. If you use the concentrations and the materials described you should get undetectable amounts of oxidation of the base polymer and only reaction with the bromine compounds. The other thing to remember is that the UV is VERY important. The UV breaks the weak bonds in the peroxide causing the formation of the active radicals. If you have an old "Black Light" pull it out and use it. Otherwise wait until you have a nice sunny day. And as soon as the yellowing is observed to be gone, remove the piece and rinse it thoroughly to get rid of all traces of the EDTA and OXY.
My feeling is that those individuals who have observed degradation and roughening of the surface of their plastic cases probably used too high a concentration of peroxide. If you stay on the dilute side and use the catalyst and UV so that only reaction with the bromine is favored, you should get an outstanding result.
As far as slowing the recurrence of the yellowing, I would suggest using a very light coating of ArmorAll or other surface protectant. It will slow the absorption of oxygen onto the surface and also reduce the amount of UV penetration slightly. It will have that slippery overly shiny feel and appearance that all surface protectants leave, but it will work to slow the recurrence of this phenomenon if that is foremost to you.