Consider setting an Expected Response Time so a reminder email is sent if the assignee doesn't complete the step in the expected timeframe. This reminder is an addition to the reminder an assignee receives when a card is un-snoozed.
Response times are added to each individual step in your workflow. Navigate to your workflow and open a step. Click, Edit Step.
The Response Time field is the only field you should edit on this page. Please do not make any other changes. A response time is not required and should be set at your discretion. Enter your response time and click Save. Repeat this for every step in your workflow.