How long can you run an APU?

I'm curious, how long can one realistically expect an APU, or Accelerated Processing Unit, to run continuously without needing to be shut down for maintenance or to prevent overheating? Are there any factors that can impact its longevity, such as the intensity of the tasks it's performing or the environment in which it's operating? Additionally, are there any best practices or recommendations for maximizing the lifespan of an APU?