quote; If the static air pressure isn't preset properly, the whole bladder is already being stretched further, and it may not last as long in use. It is flexing each time the WH cycles after you stop your hot water use
Once the system is pressurized, if its initial charge is less than or equal to the system's static pressure, the tank's air charge is at that same pressure, and it ALWAYS flexes with ANY pressure change, regardless of the initial pressurization. The ONLY time it does NOT flex with "WH cycles" is when it is at a higher than system pressure so it is only activated during the times when expansion reaches that pressure. It WILL actuate, however, at anything between 1 psi and 150 psi, (over 150 psi the tank's relief valve will discharge and release the pressure buildup before the tank can absorb it).