How long does it take to get aproval to leave and re-enter the us using the I-131 after applying for adjustment of status of a k-1 visa?

i have pretty much the same question - cant understand why no one can answer this -- what if u applied for AOS and u waiting in pretty much prison like..... - and u have to go home for an emergency - they make u wait 3 months or more to get an AP approved???? can it be such >>???????? might aswell wait for AOS.... and if u pay the fees that they are asking - why does anythign take this long - if they have a back log just hire more people - stupid system...