Well you could always burn 2 copies:
1: Burn a data dvd with the .iso file so that you will be able to just click and drag it back to your PC if you ever need to reburn it.
2: Burn a Wii copy backup using the .iso
Ofcourse, if you backup alot of games, you tend to run out of discs fast but its best if you do not have enough space on your harddrive.