Doped Ga-Sb-Ge showed good thermal stability and fast switching speed. In this work, we present the results of a comprehensive reliability study for the relationship between cycling endurance and thermal stability on a 128Mb chip using modified doped Ga-Sb-Ge material. The chip exhibited good cycling endurance > 100K cycles, and there was no fail bits after soldering test. Furthermore, the chip showed no issue for 100K cycles after 260°C baking for 1000 seconds. In terms of the data retention, it was estimated that the PCM could retain data for 10 years at 215°C after 1K pre-cycles, 210°C after 10K pre-cycles, and 205°C after 100K pre-cycles. The PCM is suitable for applications requiring high thermal stability and cycling endurance.