Let's not go to removable SSDs.

But below that portable, shock-proof Hdds and below that how reliable is storing sensitive info on SD cards? How long will they last?
I have had good experience with portable HDDs - WD, Transcend (definitely). Pen-drives, even Transcend give missing files after 2 yrs.

I guess I am trying to ask - how long can I rely on SD cards generally?
What is the largest size there and cost?