a good example of being brainwashed etc. when we went through training, there was a small group of people from a very prominent airline which no longer exists, some people having nearly 15years experience with them and they were the ones who found the training the hardest as they still had all of their old commands, procedures etc in their heads and were mixing it up with the new ones we were trying to learn. So as said, sometimes F/A experience can go against you because simply of that reason. You have already been brainwashed and it will be easier to train someone that has no experience and "old procedures" stuck in their head!
again though, how long is a piece of string?