How often do commercial aircraft go in for maintenance?

Just like laptops, printers or mobile phones, commercial aircraft eventually need to be replaced. Around 700 planes are retired every year. With aircraft, the stakes are much higher than they are with smartphones. A broken phone is a cause for annoyance and inconvenience. A broken or outdated airplane? That’s a much bigger deal. Aircraft are entrusted with the precious cargo of hundreds of lives. Their safety and reliability need to be beyond question.