How long does a PBX last?

Could you please elaborate on the lifespan of a PBX system? I'm curious to know if there's a general estimate for how long these systems tend to function effectively before requiring upgrades or replacements. Additionally, are there any factors that can significantly impact the longevity of a PBX, such as usage patterns, maintenance routines, or technological advancements? Understanding these details would be invaluable in making informed decisions regarding the adoption and management of PBX systems.