You have a busy schedule where you anticipate responses from customers so that you can process your workflow accordingly. Customers would sometimes need a slight nudge/quick reminder to look into your email. This can be facilitated by making use of an automation rule that runs on 'Time triggers' which would run once in every hour.
Please navigate to Admin > Workflows > Automations > Time Triggers > New rule.
For example, if your customer has not replied for two hours:
Condition:
Match ALL of the below
In tickets > If Hours since agent responded > greater than > 2
In tickets > If Status > is any of > Pending
Action:
Send email to Requester
Set Status as Open