But shi'te can make a mistake. Uke has to be always ready to avoid the damage, even if is unintentional.
I believe that Aikido training is a lot like kata. It is about repetitive cooperative training for the benefits of both parties improving themselves.
With that said, ukemi skills should never be under estimated. So many people focus so much on nage that they never want to learn ukemi. There should be an ukemi technique up your sleeves for anything nage throw at you, even his mistakes.
Now, with that said lol, you should be practicing to your uke's level.