The automation rule that runs on time triggers will run once in every hour and will execute the listed actions for all tickets that meets with its conditions. So, if a rule is configured to send out notification emails, it will result in bombarding the requester with multiple emails.
One way to prevent this is to introduce a flag (checkbox or dropdown, which can be added under Admin > Workflows > Ticket Fields) in the condition, which will act as an additional check for that rule.
In tickets > If Hours since agent responded > greater than > 24
In tickets > if Custom checkbox > Not Selected
Send email to Requester
Set Custom checkbox as Selected
In the above rule, the Custom checkbox field will be selected (as per the action) the first time the rule gets executed, and when the rule is triggered again in the next hour, the ticket would fail to match the condition of custom checkbox - not selected. This will ensure that the rule gets executed only once.