Our company has a Rule in place "Overdue Expense ReportApprovals". If the "Assigned Approver" (aka Manager) on the User's profile does not approve within 10 days it elevates to the next level which is the Manager's Approver (aka VP).

Example: User (Jorg) submits report to his Manager (John). 10 days pass without John approving. On the 11th day Jorg's report elevates to John's Manager, Mark. Hope that makes sense. Not sure if your company has a set-up like that.