I dunno. Short combats are probably the rarity in the games I've been in, except when the encounter was built as nothing more than a speedbump.If your fights are lasting more than 7 rounds then I suspect your games are very much outliers. DrDeth, with whom I agree on almost nothing, ran a poll on the issue some time ago which suggested 4-5 rounds were common.
Yes, that's true. But let us not say we disagree.
I had one DM that liked making them longer, so for his game, 10 rounds was normal. To each their own.