The limits on that field are minimum 0 and maximum 1000. It does not make sense to make the check run so infrequently, depending on your site's traffic it might end up running every 2 days or even less frequently. 60 minutes is a good balance — this check only takes around 0.01 second anyway. At worst you could set it to 900 minutes (every 12 hours) and only on the assumption that your site has a steady stream of traffic all times of the day.
Nicholas K. Dionysopoulos
Lead Developer and Director
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