The “industrial” cards are very expensive. SD failure has been relatively rare. About a year ago, improvements were made to drastically reduce the number of writes to the card. Since then, very few card failures have been reported and most of those were units that had been in service for several years and possibly the damage was a result of other issues that have been fixed.
The nature of flash memory is that it “wears” out with repetitive writing. Modern cards have firmware to reallocate high usage blocks and sectors, but the algorithms are proprietary and there is no practical way of knowing what the card has or how effective it is.
My home unit has had the same card for at least three years. I changed it after several years in service, copying the full contents to a new card (couple of minutes in a PC). I currently have almost six years of data on the SD.
While I expect most cards to last ten years or more, I would recommend replacing a card more than several years old if preserving history is a priority. It’s not necessary to go overboard. A standard 8GB SDHC class 10 card is fine and costs under 10 bucks. 8GB can easily hold up to 10 years of history with plenty of extra space. Be sure to read this to avoid damaging the card when removing.