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Anything under every 4 hours of checking with the time server, could put a strain on the time server if a lot of people did this. This is why there could be a chance that the time server would ban your IP address from being able to connect to the time server for updates. Anything under 4 hours is really just overkill. Usually every 24 to 12 hours is fine if you need to make sure your time is accurate each day.
With it set to every second to check with the time server, I would be surprised if you did not have higher CPU and Network usage.
Hope this helps,