You’ve identified the problem. My concern is with detection. When an approver tells me about an upcoming vacation I want to be able to see any changes to my critical path when I modify their calendar. One option, of course, is to add separate ‘approval’ tasks for everyone on the approver list but that seems like a lot of unnecessary overhead. The other approach is to set each approval task up as fixed units/effort driven and then assign all of the approvers as resources to it. That way if someone leaves town during the approval period it would impact the critical path. Is there another, better way?