Previously, S3 would default to sync every 10s when using a config
file but only every 1s when using the replica URL on the command
line. Obviously, this is confusing.
A sync interval of 1s could incur a cost of $1.30/month, however,
in practice applications are not receiving a constant stream of
writes so the cost is typically only a few pennies. This lower
sync interval will provide a smaller window for data loss in the
event of a catastrophic failure at a neglible cost.