Many people that buy vending machines don’t realize that the dollar bill validators have to be serviced on a regular basis. Dollar bill validators have rubber parts, such as belts, tires or wheels that wear out or slip over time. A good comparison as to how long these units will last is to compare them to the tires on your car. Do you drive 5,000 miles a year or 25,000 miles per year? The more you use these units the more wear that occurs on the rubber parts. Another factor is what environment or type of location these are used in. If you drive your car down a dirt or gravel road the tires will wear out much sooner than if you drive on smooth asphalt, the same principal applies to the rubber parts in the validators.