I NEVER back up until I get home. I carry 3 cameras.
I use bodies that are all Dual cards so each card is 32GB and both record at same time. Only way I will loose data is if I get shot and they steal my cameras from me. And even then, they better get the drop because I frequently carry CCW.
I get home and Download,all cards are set aside until edits are done ( next 2 days ) and all edits are on back up drives in 3 spots.
This works for me. Its what I do for every wedding and I have not lost a file in 11 yrs shooting as a pro and 400 weddings.
Your routine may vary. But my suggestion is to not take out cards from camera until you are home and ready to download......You stand a far greater chance of loosing a card then you ever will loosing data if you take the cards out of the slots.......DONT DO IT
Shoot dual cards on 32 gb cards, record to both cards at same time, dont take cards out until you are ready to DL to your editing machine, dont wipe cards until you are 100% backed up-----This is how I do it.
Hope this helps