In this talk I will demonstrate how, by introducing additional scalar degrees of freedom, one can measure properties of the inflationary era which may be otherwise inaccessible. Using two explicit examples (the curvaton and a feebly interacting model of dark matter), which introduce new informative priors into the post-inflationary phenomenology, we are able to constrain either the total duration that inflation takes place or its energy scale independently of the tensor-to-scalar ratio. Measurements of this kind may prove crucial in advancing the study of inflation if the future observational data were to yield a limited amount of new information.