I think it does sounds really bad. After one year, 26 years lifespan. We get that by doing:
30 - (30.1 - 1) = 26.
Doing that again for the next year: 26 - (26.1 - 1) = 22.4.
So you now have 22.4 years of life vs an expected 28.
etc...
30 - (30.1 - 1) = 26.
Doing that again for the next year: 26 - (26.1 - 1) = 22.4.
So you now have 22.4 years of life vs an expected 28.
etc...
That said, when someone says "it reduces the lifespan by 10%", I'm a bit skeptical of the math. Either they are not properly testing it, or the temperatures are exceeding silicon parameters.