Certificate alerts repeat every hour

I'm not sure what you mean by the 'alert setup page', alerting for expiring certificates is usually done by adjusting a cron job, see the instructions " target="_blank">here.

Of course, if you did use an iApp, there might be a page within the iApp that allows you to set the frequency of messages, but the settings there will still be simply adjusting the underlying cron job. You should probably check the cron settings directly, and see if the hourly task was updated.