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Checkpointing can be found in the rendermanrendersettings node under Rendering → Render → Checkpoint Render

Checkpoint Exit at
This method works by placing a limit on the total render time (specified with the same notation as for periodic checkpoints). The render will proceed as normal unless it reaches the time limit, at which point it will finish its current increment, write the checkpoint image and then stop rendering the frame. If there are multiple frames to render then it will simply go on to the next at this point; each frame can have its own time limit.

You can use this parameter to set a time in hour / minutes / seconds for the renderer to exit.  If a sequence of frames is being rendered, then the renderer will move onto the next frame in the sequence.

Below is an example of the format required

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