We study how the thermalization time of a single radiation cavity field mode changes drastically depending on the type of the atomic reservoir with which it interacts. The temporal evolution of the field is analyzed within the micromaser scheme, where each atomic reservoir is modeled as a beam of atoms crossing an electromagnetic cavity in which they weakly interact with the field. The cavity field thermalizes when we consider either multiatom or multilevel atom reservoirs. Under certain conditions, we find that each atomic reservoir generates a different scaling law in the thermalization time of the cavity field. Such scaling laws can be used for faster or slower heating and cooling processes. We obtain analytical expressions for the thermalization time that are verified by means of a numerical simulation of the injection of each atomic reservoir into the cavity. We also discuss how our results could boost the efficiency and power output of some quantum heat engines, during a finite-time operation, when the radiation field mode acts as the working substance.