What he says. All SSDs that failed since their release failed because of their controller and not because the SSD was worn out. Even the very first SSD drives that came available were said to last for 5-10 years depending on usage. The newer drives with newer controllers and better memory will last longer than the old ones. Also your OS will wear out the SSD more than WoW. In Windows you have always a lot of write commands when using programs. Programs and Windows can't store everything in the RAM and to not block too much space in the RAM a lot of programs write things on the HDD even if they could write it in the RAM and you can't deactivate that to 100%. You can deactivate the swap file and some things but when installing anything or updating anything (even when installing on another HDD) the installer will write some files on your OS drive because that's how the program works.
Don't be worried about WoW or any other program. Using the SSD as your OS drive is worse than any other program. When using the web browser it will save all files on your system drive and with youtube videos, pictures and advertisements on sites that are some hundred Megabytes every day you use your computer.