If you want your water dispenser to stay for the longest time, you must service it regularly. Now the frequency of servicing depends on various factors such as type of dispenser, filters used, usage frequency, and many more. But in general, it is best to service your unit every 5 to 6 months. Remember that this is just a general duration. If you suspect that the water's quality is not right, you should consider cleaning it. In short, clean your unit every month by yourself and consider professional cleaning after 6 months.