If a aint broke dont fix it I do not agree with on my life and life support! Corrosion can be hidden in your regulators. True sometimes it can be worse after regs are serviced but that is the fault of who works on them. Humans make mistakes but if it repeats maybe we should not use that shop.
It is good if you are very carefull but please read up on servicing regulators and learn from profesionals. Study service manuals and books on the proper procedures before attemping to do it youself.
WD40 is a big No!!! Food grade lubricants only where specified by the manufacturer. Nitrox or any oxygen enrichment never use silicone due to fire hazard. Cristi lube and or aproved products only.