We report performance optimization and stability analysis of aerosol-jet-printed electrolyte-gated transistors (EGTs) based on the polymer semiconductor poly(3-hexylthiophene) (P3HT). EGTs were optimized with respect to printed P3HT thickness and the completed device annealing temperature. EGTs with relatively thin P3HT films (∼50 nm) annealed at 120 °C have the best performance and display an unusual combination of metrics including sub-1-V operation, ON/OFF current ratios of 10(6), OFF currents of <10(-10) A (<10(-6) A cm(-2)), saturation hole mobilities of 1.3 cm(2) V(-1) s(-1), threshold voltages of -0.3 V, and subthreshold swings of 70 mV decade(-1). Furthermore, optimized EGTs printed on polyester substrates are extremely robust to bias stress and repeated mechanical bending strain. Collectively, the results suggest that optimized P3HT-based EGTs are promising devices for printed, flexible electronics.