Back in my day.... j/k its either hit or miss, i have seen a few Steven Pro lectures and a few others speak on fish health in LFS. and the key is: educate yourself, look for warning signs, watch it eat. all the fish that i have bought that died, i knew was questionable conditions. and i have nurse a few fish out of Ich.
but know what you're looking at when you buy. know its behaviors. ask around here, we all have opinions agreed upon or not