Projection length in months

proj_len() returns how many months the projection for each model point should be carried out for all the model point. Defined as:

np.maximum(12 * policy_term() - duration_mth(0) + 1, 0)

Since this model carries out projections for all the model points simultaneously, the projections are actually carried out from 0 to max_proj_len for all the model points.