I would not take anyone's opinion besides the foundry's
reliability documentation (you want it in writing, yes, you
do). Especially since you seem to want a specific life
expectancy, only the foundry's guarantee is worth
anything. Other than maybe a very well conducted reliability
qualification exercise (sound like fun? It ain't, even when it
comes out as you wanted).
I find the numbers unconvincing. I have looked some at
GF 12/14LPP and their nominal is 0.8V with a max of 0.9V
or so in the "overdrive" case. Your numbers are a 50%
overvoltage. And this, at less than half the L I've seen.
Taking supply from 0.8 up to 1.25V is likely to at least
double the power dissipation, already a problem in many
CPU / GPU devices and stands to compound the gate ox
reliability problem with temperature acceleration.
Check for "weasel words" in any description of these
"overdrive" modes, regarding time-in-overdrive, reduced
case temperature limits, etc. Couching reliability info in
"use model" terms has been an increasingly popular play
in the consumer electronics segment but put one toe
over the line and you can be exposed to a lot of field-
return hurt (financial and reputational). Will you accept
the "overdrive" constraints, as a product use limit that
you have to force on your customers and theirs? Mine
aren't having it - they have flowed-down environment
requirements and wouldn't be interested in any opinion
of lesser authority.