The international relations specialist said several factors prohibited immediate withdrawal. However, it was highly significant the date had been brought forward from September 2013 until some time earlier in the year.
While "desperate" not to link it to the five New Zealand fatalities this month, Prime Minister John Key was attempting a difficult balance in altering the timetable, partly an attempt to alleviate public concern, Prof Patman said.
Making immediate withdrawal impractical was the fact the Provincial Reconstruction Team had links with aid agencies, Afghan security forces, and had heavy equipment to move.
There was also the feelings of the dead soldiers' families, whose distress could be worsened by immediate withdrawal.
Prof Patman expected withdrawal to happen about March 2013.
He expected a rotation of the New Zealand troops, about 150, to take place as planned next month.
As a "good international citizen", New Zealand had a responsibility to many stake-holders in the region.
Bamiyan, once a "model" PRT because of the New Zealanders' early success, was no longer an "oasis of stability" in the troubled, war-torn country.
New Zealand could draw comfort from the knowledge there was no evidence of local support for the attacks, which suggested the Kiwis' friendly and down-to-earth approach had endeared them to locals.
Prof Patman was confident the Kiwis' legacy of economic infrastructure building, and security force training, would survive.
The increased presence of Taliban insurgents in neighbouring Baghlan was the main issue, one the Cabinet tried to address in its decision this month to extend patrols into the Hungarian-PRT province.
It was possible, although unlikely, that Special AirService troops would be secretly re-deployed to the region to improve the PRT's safety, he said.
The Taliban was likely to be testing the strength of Afghan security forces in the lead-up to the withdrawal of all countries' forces in 2014. Elements of the Taliban had also infiltrated Afghan security forces, increasing danger for foreign forces.
Prof Patman said the United States adapted to heavy IED exposure in Iraq by deploying mine-resistant ambush protected vehicles. It was possible the US would lend New Zealand the higher-specification vehicles, although it was unclear whether they suited mountainous terrain. It also depended on the level of need for the vehicles in other Afghan trouble zones.
It was possible the US or Britain needed to "step up" in Baghlan province to deal with the increased Taliban presence.
The soldiers' Humvee vehicle had IED jamming properties that appeared not to have worked, or had been outsmarted by the bomb-makers, Prof Patman said.
