How to avoid situation when associate forgets to setup vacation rules before leaving on LOA

We have had scenarios where employees go on LOA without setting up vacation rules. When subordinates submit expense reports they are stuck at manager and cannot get approved until the manager is back from LOA or expense report gets escalated to next manager. Other than reassigning to next manager manully from Workflow Administrator responsiblity, is there anyway to avoid such situations.

Thanks

User369214