I remember one time when I was visiting an out of state dojo, I attended one of the advanced classes. I was the kyu level student (still am) and my partner was shodan. I started my attacks at less than full strength as I was as yet unused to how they wanted to train.
My partner told me to really attack and to put full commitment into trying to "get" them.
After class, this person told me it was one of the most eye opening experiences they'd had in a long while. That person told me they'd learned a lot that night.
The interaction between nage and uke is where Aikido is at. Every new partner is an opportunity to learn. I believe that 'getting this stuff' to work on people that don't know Aikido or what to do is very valuable experience. You have to have control and can't rely on the other person to "know" what to do.
Yes, we need time for both training with our Kohai and our Sempai, but both should be done with equal intent. I've found that every time we get new students, I get better at doing my Aikido with the uninitiated.