It depends on a variety of factors, such as the type of wood, the amount of foot traffic, and its condition. Generally, hardwood floors should be sanded every 3-5 years, while engineered wood floors need to be sanded every 7-10 years.
If you have a high-traffic area, then sand the floor more often than usual. It is also important to check your floors regularly for any signs of damage or wear and tear, and if symptoms do occur, address them immediately with a light or call a specialist to check them.