Re: Being overly complacent as Uke
I believe there is a benefit to feeling the discomfort of a lock, stretch, or throw. I think it is important as uke to learn from the feeling since it is first-hand knowledge of the effect of the technique. Likewise, I believe the conditioning helps your body just as stretching, yoga, Pilates, etc. would. That said, I do not advocate damaging your body in extreme resistance.
However, aikido is based in striking and the thing that I thinks hurts us is that when we resist we do not learn the proper timing in which the interaction is taking place. If I have enough time to "resist" then my partner has enough time to hit me while I am resisting. After the stretching and learning, we need to transition our response from resisting to defense. Resisting is not defense. If my first response is to resist I will be unable to protect myself if my partner chooses to severely apply technique or if my partner chooses to strike instead of grapple.