| I prefer a close relationship between the amount of time a combat is supposed to represent in-game, and the amount of time it takes to resolve mechanically. One of the major immersion-breaking moments in 3rd edition is realizing that a combat which is supposed to be only a few minutes long from your character's point of view could take an hour or more to resolve at the table.
One of the interesting side effects of the much-maligned 1 minute combat round from AD&D was that it could result in combats taking about as much time to resolve mechanically as they took in-game. Five rounds of combat between a few opponents could often be resolved in about 5 minutes. | 
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