I would check once per minute. I would store the date/time of the last update in a variable. When I find the new update I would compare that against the stored previous update and verify that it has been an hour, pass or fail based on this verification, with a specific message to the test log indicating the elapsed time between the last update and the current one.
Either way, your script will be running a long time. Might as well have it report the exact time lapsed between updates.
If precision to the minute is not granular enough, you could check every second if you'd like.