There are applications which have normal and expedite service like H visa, some I140 categories, beside others. I131 has only one kind of application with No expedite service for that kind of application. Some send requests for expedite and wrote expedite on the top, bottom or any where in the envelope, others open case with local office, others keep calling ........etc. I do not think all that has anything to do with the processing of application and the time to receive FP appointment, approval or denial is hugely variable from case to case based on non logic criteria which could be predicted. If me, I will arrange my departure according to my circumstances in US and according to what I am going to do overseas not on other’s time frame for their applications.