Lack of proven stability has become a major obstacle on the path of metal halide perovskite solar cells (PSCs), in particular methylammonium lead triiodide (MAPbI(3)), towards commercial viability. This correlates with the intrinsic affinity of MAPbI(3) towards moisture and ambient air in particular, leading to its degradation in ambient conditions. We performed extensive stability tests to prove the durability of hole-conductor-free PSCs based on a triple-layer architecture employing carbon as a back contact, including outdoor tests in the hot desert climate and indoor long-term light soaking as well as heat exposure during 3months at 80-85 degrees C. These results show no evidence for device degradation under the test conditions, confirming that the triple-layer device architecture provides a promising path towards realizing efficient and stable perovskite photovoltaics.