Alerts › scripts. The number is seconds. 3600 is one hour. 86400 is the longest, a day. 0 runs again on the next announcement.
Open Alerts › scripts and press new trigger. Name it and choose Who is signed in. Cooldown is 900. That is 15 minutes before the same alert on the same machine can start this script again. A second machine is a separate wait.
Type 3600. The same alert on the same machine waits an hour. 0 runs again the next time that alert is announced. 86400 is a day, and the box refuses a larger number. Press save when this is the one you want. This shot stops before that. Cancel drops the draft.
Where it runs is Run a script on the machine that raised the alert. Which kind starts it is Run a script only when a disk fills. The first announcement still waits for the usual delay so a flap can clear first — Run a script when an alert opens.