The easy answer is as needed. The frequency of service depends on the demand. In some places we go three times a week and in others once every two weeks. We plan to service them when they are around 20%-25% empty. How empty is empty? The answer is different for us than it is for our customers. Sometimes we get requests for service when the snack machine has one empty line (1 out of 32+). I understand that as a customer I want to see all options available, and for that reason we always strive to have all lines filled at all the time. However, servicing the machines when only one or two lines are empty is not a good way for us to maximize profitability. Since not all lines are used at the same pace, the best time to service them is when they are at least 20%-25% empty, which is roughly the same as 2-4 empty lines. If a line sales super fast compared to the other, we add a second line of the same product to make sure the product is always available. For example, in one of our accounts, the cynamon rolls were gone in two days while the rest of the items were almost at the same level. Servicing the account just to add more cynamon rolls was not efficient for us, so we added a second line of cynamon rolls and now all the items sell at the same pace.