Well, it took me about 2 months of active working time to finish my first animation, which was about a minute and a half:
http://www.newgrounds.com/portal/view/474831Just over a year in total, because I only worked on it sometimes. That included about 4 weeks of painting all of the backgrounds and characters, with the rest of the time spent learning Flash from scratch, animating, and several very frustrating days of fiddling with actionscript for the snow effects.
It used the digital cutout technique, which is apparently supposed to be really fast-paced.
However, the digital cutout technique can also be one of the most complex forms of animation there is. For example...
http://www.youtube.com/watch?v=TrUfp2tK3ag