Thanks for writing in!
You could potentially accomplish what you're after here by setting up an alert that is *guaranteed* to fire - and then adjusting the "max send" frequency to meet the time period you're looking for.
We'd recommend setting the "alert when" parameters to something pretty low (that will guarantee it fires) - and set the "notify" option to "each time alert conditions are met." If you set the "maximum e-mail frequency to send" to 60 minutes - then you'd get an email every hour for every target you associate that alert with (and you can specify a different frequency here if you'd like).
If you have any questions, or if you were looking for something different that what I've proposed here - please let us know!