I am still not sure how you achieve this condition "Execute the Rule 48 Hours since last update" under Business Rules but based on the DueByDate you can configure SLA Escalation mails under Admin\Service Level Agreements.
Maljeev
SDP Support - FAQ
ServiceDesk Plus - Help Desk Software of your Choice
Maljeev
SDP Support - FAQ
ServiceDesk Plus - Help Desk Software of your Choice