Time Marches on...
1. The previous years offensives, although having limited early success, were disastrous in that large numbers of Tali fighters and key leaders were killed. This was in part due to their attempt to move in larger formations - hence early success in remote area - leaving them sitting ducks for allied airpower once allied forces moved into the area. Thus they have few qualified leaders and even fewer fighters. Those fighters that remain are probably demoralized due to the defeat of AQ in Iraq.
2. Pakistan unrest. With the change over of government and the ongoing turmoil of national leadership, Tali/AQ and Paki fundamentalists are creating mayhem across the country. This secures Waristian for Tali/AQ ops bases, while directing forces into Pakistan rather than Afghanistan.
3. Indicators that the US is preparing a mini-surge style campaign to preempt any Tali spring offensive.