I voted 45 minutes, but I would have liked to vote for a 30-45 minute range. We've had some zippy encounters in
4e and some that bogged down, but the majority have fallen into this range. Our very last combat was fairly short; we decimated a whole party of orcs in about 20 minutes. I've noticed two factors have contributed to long ecounters: one, our striker, who is admittedly an under-optimized star pact warlock, can't hit anything, and two, truthfully, bad encounter design on the part of the DM (incorporeal wraiths against a 3 man party that has a relatively low DPS due to problems with our striker).
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