Whenever you use any of the 'Hours since..' options under conditions, you will have to restrict your conditions to a timeframe. If not, the rule will keep getting executed every consecutive hour.
For example, if you want to send an email to the agent if the hours since requester responded is more than 6 hours then setup the following:
Match ALL of the below
In Tickets > If Hours since requester responded > greater than > 6
In Tickets > If Hours since requester responded > less than > 7
Send Email to Agent