Abstract Two-dimensional semiconducting materials such as MoS2 have gained significant attention for potential applications in electronic components due to their reduced dimensionality and exceptional electrical and optoelectronic properties. However, when reporting the performance of such 2D-based devices, one needs to consider the effect of the environment in which the characterization is carried out. Air exposure has a non-negligible impact on the electronic performance and vacuum thermal annealing is an established method to decrease the effects of adsorbates. Nevertheless, when measurements are performed in ambient conditions these effects arise again. In this work, we study the changes in the electrical and optoelectronic properties of single-layer MoS2-based devices at air exposure after thermal annealing treatment. Measurements are carried out in an in-situ vacuum thermal annealing system, enabling the recording of electrical performance degradation over time. Moreover, this work shows how hexagonal boron nitride (hBN) capping improves device performance, both in vacuum and after venting, as well as stability, by decreasing the degradation speed by around six times. The results suggest that vacuum thermal annealing and hBN capping are methods to mitigate the effects of air environment on these devices.