<p>The stability of thermistors determines the precision and reliability of the electronics, representing a critical constraint for high-precision applications. This study investigates spinel- structured Ni_<i>x</i>Mn_{1.13-<i>x</i>}Co_0.74Fe_1.13O₄ (<i>x</i> = 0.12, 0.18, 0.24, 0.30 and 0.36) NTC thermistor ceramics, systematically examining the effects of Ni/Mn ratio, sintering process, and annealing treatment on the electrical and aging characteristics. Experimental results show that increasing Ni doping content (<i>x</i>) promotes preferential occupation of Ni²⁺ at octahedral B-sites, driving the oxidation of Mn³⁺ to Mn⁴⁺ for charge balance compensation, thereby significantly reducing room-temperature resistivity from 3.75 × 10⁶ Ω·cm to 2.11 × 10⁴ Ω·cm. Optimal aging resistance (4.42%) was achieved at <i>x</i> = 0.18. Sintering temperature studies revealed that samples processed at 1180&#xa0;°C for 4 h exhibited superior comprehensive performance: material constant <i>B</i> reached 3829.24 K with resistivity of 2.45 × 10⁶ Ω·cm and aging rate of 4.46%. Further annealing treatment (860–1100&#xa0;°C) of Ni_0.18Mn_0.95Co_0.74Fe_1.13O₄ ceramics sintered at 1180&#xa0;°C effectively reduced oxygen vacancy concentration, decreasing the aging rate to 0.81% while maintaining excellent electrical properties (<i>ρ</i> = 4.35 × 10⁴ Ω·cm, <i>B</i> = 3278.21 K). This study developed a multi-scale control strategy encompassing composition design, sintering densification, and defect elimination. Utilizing this strategy, the material with a composition of x = 0.18 exhibited optimized electrical properties (resistivity <i>ρ</i> = 10⁴ ~ 10⁶ Ω cm, B-value &gt; 3000 K) and stability (aging rate &lt; 1%). This work provides engineering-guided process guidelines for developing high-precision thermistor components.</p>