In Hong Kong and Bangkok, gate information is always available 2-3 hours before departure, with last minute changes possible but always at least 45 minutes in advance.

In London Heathrow, the gate information is not available to public until 45 minutes and sometimes 35 minutes before departure. However, BA system could tell the gate information at least 1 and a half hours before departure in MOST cases. I believe other airlines are the same in LHR that their back door management system will tell them which gate it is hours before departure.

The reality for slow in displaying the gate information is the greedy BAA. T5 was designed in such to maximise the profit of retail space and revenue. All passengers rather than flying F class are forced to wondering around the duty free shops before the gate. By not displaying the gate information until last minute BAA can force many non-status passenger remain the central retail area. T3 and T4 is the basically the same. T1 is less so at this moment but the new T2 would be the same set up!

Regardless how often last minute gate change happens, 40-45 minutes before departure for gate information is just in sane. I guarantee you when you ask any lounge dragon, they will be able to tell you gate information earlier than BAA screen if they know how to look for the info.