The Burj is a bit of a waste of moeny in any case. Why not find a hotel that can extend your check-out ill 6pm (perhpas by paying 50% surcharge and having a leasurly diner before goign to the airport. Most hotels would also let you use the pool/health club till 8pm (before diner) even after you have checked out. I would just pick on of the 5 stars - most of which are competitively priced.