I would like to add that it is not the airline who choose the gates it is Air Traffic Control who make the decision and last minute gate changes are common everywhere as planes might be delayed and the gate isn't free at the time it is needed so planes need to be diverted to other gates. This is all under the control of ATC, not the airlines. so it's always best to stay near to a monitor and be prepared to run. Done many times even as cabin crew! Having said that I do think decent airlines will make concessions for last minute gate changes and I've always found this to be the case with Emirates, Virgin and BA.