We just did that last month with guests - bought tickets for just before sunset so we could see daylight, sunset and night (and fountains!) It was perfect! I did have a bit of a scare, though, 'cause the queue was MUCH longer than it was the first time we went and I thought we were going to miss daylight and sunset, but it ended up being fine. We bought tickets for 17:30 but that was the beginning of Feb, forget what time the sunset was then.
There is no limit on how long you can stay at the top, just be prepared to queue to get back down again.
You will be fine... Don't think there is a time limit once you are up. You just get the lift down when you're ready.... Enjoy!
Thank you Captainjacky! I thought maybe you only have half an hour since they are selling tickets every 30min.
Can someone please tell me how long you can stay at the observatory deck in Burj Khalifa. Thinking of going next week at 6pm and need to know if I will be able to see sun set plus night light ;)