After we have majority committed the progress. This will keep the storage space consumption of the resharding recipient in control in the expense of adding more stress to the storage engine. If the user can afford it, it is usually better to just wait for resharding to complete and have the collection dropped during cleanup.

Note: We should get some data on how big these oplog buffer collections get on long running resharding operations. If it is not very significant, then it might not be worth doing.