Pre booking for burj Khalifa is must. Otherwise there are no tickets available for the peak time. You can stay as long as you want at the top. It is best to be there an hour before sunset so we can enjoy every view. I.E before sunset, at the time of sunset and after that. Each view has its own charm. I booked a slot of 4;30pm and was there till 8pm. I made the most of it. Sunsets are my favorite and so it was from burj khalifa. They do offer an upgrade from 124th floor to 148th floor for more money but it hardly makes any difference. Dubai from the top is one time view.
An interesting peek into the past, the Heritage village also provides a backdrop for the Bedouin lifestyle and culture. It depicts what a typical oasis village would have looked like. There are several small shops where artisans display hand crafted goods and are great place to collect some souvenirs to take back home. You even get a chance to see how these craftsmen work. Live animals traditionally used for transportation are also available for viewing. There is an open museum here that depicts the desert life here before the city was developed. The restaurant inside Heritage Village serves great Arabic dishes and offers breathtaking views of the city. A visit to this place is recommended before 5 pm as most activities shut here post that.