Um, reading of a SD card doesn't hurt it, nor does writing to one. It's just erasing data from SD, of which, most commercial cards can handle 100,000 erases per sector. So if you buy a 32 GB card, and use only 1/4th of it at most, you get 4x the life out of it, which would be at least 400,000 days worth of erasing one game a day, or about 1,100 years.
Do you plan on living for 1,100 years? If so, then perhaps you should back up your flash memory :lol
Edit: Furthermore, the Wii's system memory is flash memory anyway, so if you are really worried about your memory stick, rest assured your Wii itself will go bad long, long before your SD card, as it is accessed much more frequently.