A set for each 5D. I wouldn't fill it but I always stay on the side of caution so get more than enough. 64G each would've been enough if I shoot 50/50 even for each camera but the fact that I shoot more with the camera that has the 35mm on so I alway end up one camera having more and one less. Now with this i don't need to worry.
I also have a bunch of smaller CF cards and 2 x 128 SD...the reason for this is I have 2 back to back weddings (so 4) this year and I don't have time to back up the shoot in between. This way, the back up is done on the fly.
As long as you don't loose the memory card/s and/or there are no data corruptions.
You're getting married 4 times?
![Stick Out Tongue :p :p](/styles/default/xenforo/vbSmilies/Normal/tongue.gif)