This work studies the effects of thermal stress on Dynamic Random-Access Memory (DRAM) retention-based Physical Unclonable Functions (PUFs) based on Commercial Off-The-Shelf (COTS) Single-Board Computer (SBC) modules. Our results show that prolonged thermal stress, in general, leads to a decrease in the entropy of the responses of this PUF (as the number of bit flips is reduced) and a loss of its reliability (as responses taken before and after the stress has been applied to this PUF do not adequately match each other). Nevertheless, we note that as time passes after we stop applying thermal stress to the relevant PUF devices, their responses start to resemble more and more those that they produced before thermal stress was applied to them. As prolonged thermal stress has been utilised in order to induce artificial aging on electronics, our work not only studies the potential effects of aging on such electronics as DRAMs in general and DRAM PUFs in particular, but also sheds some doubt on the ability of this method to induce permanent effects that would truly resemble the effects of aging.