Given from what I heard about how long it takes to run ONE combat in 4e, wouldn't that take like, weeks of gaming?
It sure can if you let it.
I have quite a bit of 4e experience at this point in time.
Ran a weekly game for 2 years, 6 hour sessions. Plus a few other campaigns of various lengths sinse 4e was first released. As a result, I have done a ton of combat encounters with 4e.
So, my assessment is that a combat can take forever if the gm is doing it wrong, and the players are 'slow/unprepared'
With experienced players, and experienced dm, the big combats took 1-2 hours depending on complexity.
I have experienced lengthy endless 'bang your head on the table' 4+ hour combats in 4e games as a player, but not as a gm.