I'm a bit new so maybe this feature exists but i couldn't find it.
But while i'm trying to animate simple things such as a walk or run cycle i find myself frequently ctrl-c, ctrl(-shift)-v-ing the first frame of the animation towards the end of the animation.
Is it possible, maybe somewhat like the way you use modifiers to mirror meshes to use something like modifiers to mirror/copy your keyframes as well, so you don't constantly hace to copy and paste to update the second half of your animation?