Dead Things, Mikey, Dead Things. . .

It all started 10 days ago.
Day 1: It was Sunday night and Randy and I noticed a foul smell in the boy's room as we were putting the boys to bed.  I decided I'd deal with it in the morning and promptly forgot all about it.
Day 2:  I opened the door to the boy's room when my nose was assaulted with such a horrible smell I found myself gasping for air.  It only took a few seconds to locate the source from whence it came as the warm, putrid air wafted out from the air duct in the corner of the room.  I quickly closed the vent and escaped as fast as I could.  It was obvious some type of rodent had died down in the air duct.  After getting the boys off to school, I quickly opened the windows in their room, closed the door tight, and threw a blanket on the floor covering the crack under the door and hoped that the some fresh air from the open windows would magically solve the problem.  I was wrong.  Before putting the boys to bed that night, I dumped some bleach down the vent which made the room instantly smell like a blend of bleach and dead animal carcass.
Day 3:  By this time we'd gotten into a routine of spending as little time as possible in the boy's room and  kept the door closed at all times.  I got brave and removed the vent from the floor, stuck my camera down in the hole and took a picture, hoping to see the cause of the smell.  No such luck as the photo revealed just a bunch of dust and debris.  Then I got even braver and pulled out my amazing new vacuum and shoved the hose down in the depths of the air duct as far as it would go, all the while trying not to throw up.  But that didn't work either so I dumped some more bleach down the vent and left.  That night we kept the windows on both sides of the room open, creating a very cold draft of air, and piled warm blankets on top of the boys.  (They get used to the smell after a few minutes and let's face it, they're boys.  They usually smell too so it's not like I was torturing them by making them sleep in their room.)
Day 5:  I call this The Day of the Miracle.  We received an envelope in the mail full of random coupons. Strangely, I decided to look through the coupons and came upon an ad for air duct cleaning.  Until that moment, I never knew such a service existed.  The add included a coupon for 75% off.  I was so happy I literally felt a chorus of angels singing "Alleluia."  I quickly called for an appointment and explained we need their services ASAP as there was something dead in our vents.  The earliest they could send someone was Monday, five days away.  So the waiting game began.
Day 6:  The smell has now spread to the family room below the boys bedroom.  Now that vent remains closed at all times.
Day 7:  I happened to be in my room across the hall as Ethan was about to get dressed in his room.  He didn't know I was watching as he karate-kicked the door open, threw his arm over his face to block the smell, ducked his head, and ran into his room as if he were running into a fire.  He made horrific gagging sounds as he scrambled to find some clothes, then ran back out to the hallway to dress.  I was laughing my head off and told him it would all be over in just a few more days.
Day 10: The doorbell rang at 4:45 pm.  The air-duct guy was here and he was even early.   I beamed with relief that the nightmare was about to end.  Randy showed the guy our coupon and walked him to the furnace.  Then the guy asked to see every vent in the house, making tick marks on his clipboard as he went.  Both Randy and I tried to tell him we weren't worried about the other vents, just the one with the bad smell.  Finally he entered the boys room.  He looked down inside the duct then asked Randy to turn on the furnace.  As soon as the warm, stinky air hit his face he started screaming, "Turn it off!  Turn it off!" He pulled his shirt up over his nose and was out the front door in record time.  "I vacuum dust.  Not dead animals!"  He mumbled something about renting a camera from Home Depot to find the problem and then he was gone.
So now we are back to square one.  How long does it take for a carcass to decompose?  Surely it can't be  much longer.  We've found Febreeze helps a lot in the meantime.  Has this ever happened to you because it's a first for me.