Puppy Survival Guaranteed at 100%?

Does anyone know if puppy survival is definitely guaranteed at 100%?

I really want to customise two of my pups but I don't want to spend that GC if there's a chance they won't make it to adolescence ;o; 

Yep! It is definitely guaranteed, your puppies won't die as long as their survival chances are always at 100% :D (confirmation of this is on the Help page, pup survival section)