For domestic flights it is supposed to be "up to 3 hours" (International is up to 4). We have used ME at least 10 times, and this is the only time it has ever taken more than 3 hours after the flight landed for the luggage to arrive at the resort. I looked at the FAQS on Disney's website and they currently state that it is "up to 3 hours" after arrival "at the resort" (I could swear they used to say up to 3 hours after your flight lands- but I don't know how long ago that was). I know that we were checked into Yacht Club before 9:00 p.m. because we had a club level room that had a view of the EPCOT fireworks, and we were in our room before Illuminations started and we watched it from start to end from our Balcony, so they definitely did not make the "up to 3 hours" posted on their website. We had our arrival drink and snacks in the lounge before heading to the room, too (FYI we had never stayed club before and the CMs on the YC club floor are fantastic! I think we got spoiled- it will be hard not so stay club level in the future!)
It could be a whole lot worse though. My friend who went last May stayed at YC resort checked her family's luggage for the trip home and it never arrived at home. The airline originally told her they thought it would show up, and then when it had not shown up after a few days they claimed that they don't think it ever actually got to the Orlando airport from the resort. I told her to try to get ahold of WDW to see if there was a possibility that it somehow got mixed up and held at bell services and was still sitting in storage at the resort instead of being put with the bags that were resort checked and headed to the airport, but she never got anywhere with that. The sad thing was other than what they brought back in their carry-ons, her 3 boys lost all their souvenirs from the trip. So, the fact that we were up a little later than we planned to be that night was no big deal!