For practical applications, there are several points of interest in the numerical simulation of transient Thermal Elastohydrodynamic (TEHD) lubrication. Among others, is the possibility to investigate the impact of transient effects depending on the dynamic characteristics of the contact. In this regard, the paper presents an original study on the characteristic times involved in a generic line contact lubricated with a non-Newtonian fluid. The paper highlights the dependency of the dominant heat transfer mode on the Slide-to-RollRatio(SRR), leading to the formulation of new thermal characteristic times. Based on results from time-dependent computations, it also provides a criterion linking the onset of transient effects to the dominant thermal characteristic time which has been validated on various operating conditions.