The actual test programs for most parts add a fudge factor to
add margin to the test. And the characterization data for a part
also has a margin added to it. So essentially most parts go out
the door with much more margin than simple datasheet limits.
I at least know this was true of test programs many years ago,
a 20% fudge factor was used over and above all known data,
process variation, characterization, T & V......
Regards, Dana.