I'm fairly new to pond ownership, so I'm certainly not one to be dispensing advice. I don't know how common it is...but, I would assume transferring fish into a new habitat is about as traumatic to them as it can get.
So, I guess if they are going to die, it would be shortly after being stocked...especially if their new home isn't up to par. (oxygen, hardness, ph, etc.)
In all honesty though, I've seen fish do just fine in some rank ponds, so my biggest concern when buying was the trip itself, not the pond. I figured some would die since it was going to be an hour drive, but they didn't. So, I'm not sure how long they can safely travel in the relatively small bags they put them in when you purchase. I wouldn't push it much longer than an hour though.
To address what Bill said above, yeah you want to acclimate them to their new home. Put the bag in the water on its side and slowly combine the water. If the fish swim out on their own, they're good to go. If they try to stay in the bag, keep combining the water slowly until they swim out.
