Bicycle maintenance is seriously important to a professional biker. However, how often should you give your bike a complete maintenance? A month? A year? I can state that it depends on a lot of outside factors. The first factor might be the frequency you use your bike. The more you use it, the more you need to maintain your bike.
Another, the terrain you cycle on is also important. If you often ride on rough terrain, you should frequently take care of the wheels. Last but not least, this is your budget. if you do have much money to go to bicycle center, you can learn some techniques to maintain your bicycle at home.