Adding to what mecabq says, I often pop out of the airport when in transit (and always less than 6 hrs). Now that QR allows you to check-in online you can reduce the amount of time you need to be at the airport before the flight. The new museum of Islamic Art is also well worth a visit and located at the beginning of the corniche. if there's no traffic, you can be there in 10-15 mins from the airport.