Reservoir Pressure Calculation

Good morning Pet people

i have one question:
in order to estimate reservoir pressure from ESP downhole gauge sensor @ certain depth or from static fluid level, we need specific gravity "SG" of oil, water and gas.
this SG was usually calculated from static gradient survey. But every time we get a different value of this SG from static gradient to an other or comparing to PVT sampling.
After many years producing and in order to get the most appropriate reservoir pressure, should we use value from PVT or from last calculated value from static gradient survey?
please i need your help!
regards