Postdoc position: should I stay for one year or two years? I am currently a PhD student who will graduate in July.
I am currently applying for academic postdocs,
with the goal of taking a tenure-track job at the end of my postdoc position.
In my field (operations research),
most of the postdoc positions are for one year
with a possibility of extension to two and sometimes three years.

If I am given the choice, should I spend one year as a postdoc, or two?
Would I be able to make a significant contribution to a research project if I were to only work as a postdoc for a year?

Currently, I am leaning towards a two year postdoc.
If I were to only spend one year as a postdoc,
I feel that it is a rather short period of time
in which to start and finish a research project.
If I spend two years as a postdoc,
then I would be applying for tenure-track jobs one year later,
and I am also hopeful that at that point,
I would have done some research which I could submit in my job application
in addition to my existing PhD work.

What advice would you have for me?

Edited in response to question in comments

As David Z mentioned, in my field, a postdoc appointment is for a fixed term  (typically one or two years, or one year with a possibility of extention).
Two.

In the United States, at least in computer science, most postdocs are synchronized with the academic calendar.  A typical postdoc starts in August, and faculty application deadlines start in November.  So for purposes of applying for faculty positions, a one-year postdoc is really only three months long.  A two-year postdoc gives you five times as much time to strengthen your faculty application!