please do, it's wrong.I'll just tear out that page of notes I took in my HOG reg service class.
Pistons first stages tend to corrode easier because water will surround the spring and piston if not fully filled for a environmental kit. That said, piston regs at the seat and piston interface in my experience historically hold a better seat than diaphragm regs. That is changing with better material used in HP seats for diaphragm regs.
the spring on a piston reg can lose it strength over time, unless defective however we are talking ears and thousands of dives. During which the reg will get serviced and adjusted anyhow and if the spring cant meet spec changed out