So, say for a 20-second-long scene, you want to have someone waving in the background the entire time. You've accomplished the animation for one wave, but some issues:
-If you're using copy/paste, how can you be sure the starting point is the same as the endpoint, rather than just eyeballing it on the timeline?
-Is there any easy way of extending the length of the animation (via looping) rather than just copying/pasting a bunch of times?
-Less likely: Let's say late in your moviemaking, you decide that the wave doesn't quite look right, so you make one change. Would you have to redo all your duplication work?

The best way I can think about what I'm looking for is like the Repeat effect in Audacity. You select a strip of audio, then tell it to Repeat, say, 10 times. The audio will continue end-to-end in a loop that way.

This is easily handled if you're taking in a Sequence from the game animations, but not if you're doing the animation in the motion editor.