After Toolkit > Modifiers > Simple Loop
Loop layers with one button in After Effects
Make your footage loop forever.Simple Loop makes your selected layers indefinitely loop through time remapping.
Simple Loop - Quickstart Guide
Open your After Toolkit, select your layers, and click on Simple Loop.A cycle loop applies a regular loop: your layers start again from its first frame after its last frame.
A ping-pong loop applies a back-and-forth loop: after their last frame, your layers play backward, then forward again, and so forth.
You can extend your layers in the process to make them fill your timeline.
Simple Loop works with footage and precomps, as it creates a time remapping expression.
