Does analysis at two points in time count as 'longitudinal'? According to whatever norms and expectations exist in the econometrics literature - if an analysis looks at two points in time can this be described as longitudinal, or would more time slices generally be expected for work that describes itself as such?
Yes,  A longitudinal study involves repeated observations of the same variables (e.g., people) over short or long periods of time.   You can have more than two points in time for your project.  It really depends on your study's converge (time periods under analysis).