They can get it painfully wrong last time. I came down with something like optic neuritis a few years ago. It's often one of the first signs of MS in many folk. When I googled something like "MS life expectancy", the blurb said something like "3-7 years" -- with subtext indicating it's 3-7 years LESS than average rather than "you're kicking it in 3 years".

Turns out I didn't have optic neuritis.