Under normal circumstances, a mattress should be replaced about every 6 to 8 years. However, keep in mind that this is just a general guideline and not an absolute rule.
Fact
Mercedes invented a car controlled by a joystick.
The joystick in the 1966 Mercedes F200 showcase car controlled speed and direction, replacing both the steering wheel and pedals. The car could also sense which side the driver was sitting in, so someone could control it from the passenger seat.