As a person who is always "up for it" I took a while to come to terms with the idea that people who are new/slower/less able than me have as much right to their time in the dojo.
If they are irritating us then we have something to learn as to why it bothers us so much. People who donīt "cooperate " or seem "lazy" should not be taking away from our aikido experience, they should be enhancing it.
Its great fun to practice at high speed. Launch our aikido buddies as far up the mat as we can muster and then launch them again but is this martial arts?
Surely the real challenge is in throwing someone who has resisted. For me I am happy knowing that they could not resist me because when I practice slowly I feel every slight movement. I cannot be resisted. I change vector, direction, speed and wham! Too late mate
More difficult but infinately more rewarding...