Nowadays, heavily doped pi-conjugated polymers via ionic doping play a crucial role in devices such as organic electrochemical transistors(OECTs) and thermoelectric(TE) devices, where high on-current is required. However, the stability issues of ionic doping remain unsolved, since active layers in such wearable devices must be continuously exposed to electrolytes, which makes encapsulation infeasible. In our research, we fabricated poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene](PBTTT) films via ion-exchange doping. Their long-term conductivity under various stress conditions, including heat, water, ethanol, ambient, and inert atmosphere, was measured. The results were then analyzed from two aspects, doping stability and structural degradation. This work gives the key mechanisms underlying the conductivity decrease and guidance for designing robust polymer-based electronics.