Emirates is not the only airline to do something like this (i. e. let passengers wait 3+ hrs then tell them the flight is cancelled. It was on a Norwegian Airlines 787, OSL-MCO. The flight was scheduled to leave at 4:20pm. They began boarding at 4:50pm. We were ready to push back at 5:15pm, until there was a problem. They never told us what problem was, and it was until 6:00pm when the captain said "We are encountering technical difficulties, please wait for 10 minutes before we take off." At 6:15, they began flashing the mood lights different colors which bothered the crap out of me. At 6:30pm, the captain said "We should be able to take off at 7:00pm." No announcement until 7:30pm, the captain said " We will deplane everybody, as it is suspected to take more than an hour to fix." Everybody is waiting in the terminal. By 9:00pm, one flight attendant comes out from the jetway and quietly says that the flight is cancelled. Only like 20 people heard what she said. Eventually the next day, they rescheduled the flight to 8:00am the next day, which eventually got delayed to 4:00pm the next day, so like a 24 hr delay.
Back to my point,
This was an elapsed time of 5 hours at the hub!!