Continuum approximation has often been used to develop the overall lumped kinetics of a huge number of first-order reactions. However, this approximation can give rise to some conceptual and mathematical problems when applied to mixtures in which the individual reactions are non-first-order. Recently, three different approaches have emerged to tackle the problems. The present paper attempts to put the three approaches in perspective. Also, the continuum approach is used to find the optimum temperature strategy for converting continuous mixtures subject to catalyst deactivation.