3) Two springs in parallel have a lower oscillation period than a single spring with the same spring constant. That allows the regulator to be more precise and faster to react to any changes in pressure.
Originally Posted by Menace_AO
4) All springs wear out if the number of oscillations above a given stress level are exceeded. Most springs should handle millions of cycles within their parameters if the fatigue levels are not exceeded. that is much more than the life of a mag valve, especially since these springs don't move much.
5) The early RT, retro, emag valves had the single on-off hole to cut down on the parts needed. It eliminated one oring. Later emag and retro valves and all X-valves went back to having two orings. I suspect it was because the machining process was much easier.
6) The threading on the retro valve bodies is different from the classic bodies so that you can't install one on the other by mistake.
7) Yes, the back cap is stainless. Good cuts of lots of very fine threading allows a good mate between the threads. The number of threads in contact with each other is a high number which reduces the amount of force on any one point. The spread of the force over a large area keeps the force threshold below the value that the oxide layer breaks down which prevents it from wearing out.
Except for the Automag in front, its usually the man behind the equipment that counts.