To exploit the desired properties of molecular polaritons, we need to preserve the hybridized state for the duration of the relevant quantum process. The key measure is therefore the degree of quantum coherence, which characterizes how long the quantum states involved can interfere with each other. It has been shown that interactions of the molecules with the environment, such as cavity loss or phonon-induced decoherence, occur rapidly on a timescale of several femtoseconds and this constrains the ability of the molecular polariton to last throughout the desired quantum processes. However, previous work has shown that coupling a single molecule to a cavity significantly enhances the coherence lifetime of the hybrid light-matter system. Furthermore, recent work has established that coupling many molecules into a cavity reduces the effective reorganization energy of the polariton states. This collective coupling effect reduces the coupling strength between the molecular electronic states and their respective phonon modes, and thus impacts their coherence lifetimes.