However, to ensure we actually learn something and don't always get injured, we train in a repetitive and cooperative way.
I (personally) feel that I have to try a technique many times in a sparring situation before I will feel comfortable with it.
I for one would never do "Aikido sparring" with you unless I know that you have already some years of cooperative Aikido training under your belt.
The problem is that unless you learned the proper sensitivity for your partner in cooperative training, you're very likely accidentally injure him when tempers go hot, when under pressure etc.
Just yesterday I was training shihonage with a friend (he's been doing Aikido for 6 months, I'm in for one year now), and *twice* he almost broke my arm without noticing.
As this was in cooperative training, I could yell at him before anything serious happened. In a "sparring setting", well, bad luck...
A punching/kicking martial artist can give me bruises, make me bleed and eventually break my nose or so during sparring - and protective padding helps rather well against all this. An Aikidoka can rather easily break my arms/legs/shoulders/hips, snap my neck or crack my skull - and this can happen accidentally
unless he knows both how to execute the techniques peoperly and how to have a "feel" for Uke.
Ukes should be re-usable ;-)