Solid-state reactions and phase transformations in which the activation energy changes with the extent of conversion, e.g. multi-step or dispersive kinetic processes, cannot be reliably treated using current thermal methods, particularly when it comes to handling non-isothermal data sets. New models that consider distributed reactivity and/or the potential temperature-dependence of the pre-exponential term in the Arrhenius equation are urgently needed and, based on them, the extension of current theory to appropriately treat non-isothermal data. Numerical methods could prove useful in overcoming the variable-separability problem that can hinder the analytic solution of more complex kinetic relationships.