It could be a good idea to do a full overwrite operation to a SD card as it then will check all memory cells if they are fully functioning. It does the same thing when used in the scanner, when the scanner saves something, even a single byte, it will always go to the next cell in the card and if the readback show some inconsistency it will mark that cell as bad and not use it again. If you leave data untouched for a very long time, maybe one of the favorite lists are never changed, then if a memory cell starts to go weak and gets harder to read then it will not be any reaction to it, just a read error. If you always do a "clear user data" to clear all data off it, or the full overwrite, before programming it will then be able to sense if a cell are bad. So maybe once a month do a full overwrite. Most SD cards can handle ten thousands of full overwrites without wearing out.
/Ubbe