I don't understand why some seemed to think that the Iraq conflict would be shorter than the Afghanistan conflict. It took from October 7, 2001 until November 13, 2001 for the Taliban to be kicked out of Kabul - 5 weeks, according to the [link|http://www.wikipedia.org/wiki/US_invasion_of_Afghanistan|Wikipedia].
I expect Saddam to hold on as long as he can, but do - like you - expect his military support to collapse reasonably soon. My guess would be the main conflict will be over within another 2-3 months, rather than 2-3 weeks though.
Cheers,
Scott.