I've kept an eye on mine and after a couple years it's still going strong with no leaks or anything."Dang fuel pressure was at 30psi after all that only upped it to 35psi"
Has your gauge been calibrated? Gauges are very commonly out quite a bit.
Using the Shraeder valve as an attachment for a pressure gauge is okay for testing, but pretty risky for any extended time, as the connection is weak and relies on a rubber sealing ring.
A better way is to get a spare fuel rail and silver solder on some 1/8 NPT fittings.