Assume that the GFCI receptacle is not subject to unusually high levels of tripping.
When I say "the life expectancy of a GFCI receptacle", I more specifically mean, "the life expectancy of the GFCI circuitry found in a GFCI receptacle."
A GFCI receptacle will continue to power items that are plugged into it, even after the GFCI function no longer works. But, I am concerned specifically about the lifespan of the GFCI function.
To verify its GFCI function, I do not exclusively use the "TEST" button that is built into the receptacle. I rely on a standalone GFCI outlet tester that trips the GFCI receptacle.
I have noticed, just in my own house, that all 3 outdoor GFCI receptacles currently have non-functioning GFCI circuitry, while all of my indoor GFCI receptacles function perfectly. I assume that exposure to water and the high humidity of the great outdoors, plus the extreme temperatures, are responsible for shortening the lifespan of the GFCI circuitry.
Hence, it would be wise of me to split this question into two:
What is the life expectancy of an indoor GFCI receptacle?
What is the life expectancy of an outdoor GFCI receptacle?